Success sat on Big John Corcoran like antlers on a bull elk. Six-foot-four and built like a fullback, he sported a mop of gray-blond hair, a speaking voice that played bass fiddle on a listener's bones, and ice-blue eyes that lit up like headlights when he switched on the charm. With energy, presence and a flair for the dramatic, he survived college and graduate school, became a respected social-studies teacher in Oceanside, Calif., then turned a $2,500 investment into a house-building business employing more than 200 people. At 48, Corcoran was a multimillionaire who owned a $600,000 villa with a slam-dunk view of the Pacific, went off on European vacations with his attractive wife, Kathy—and lived in terror that somebody might expose his unspeakable secret: He was a total illiterate.

"Reading," he now admits, "was to me like looking at Chinese, at scribbles. I couldn't get the letters and the words together. And the higher I climbed, the harder it became to expose myself, to ask for help. They'd have thrown me out of college if they'd known, and who would employ an illiterate teacher? I was trapped. If the truth got out, how could I support my family? So my life turned into a nightmare. For 40 years I lived like a fugitive. There was no day I didn't dread that someone would find me out."

Incredibly, nobody did. But two years ago Corcoran finally turned himself in. He showed up at an adult learning center, asked for help and got it. Now literate at last, he has taken to the lecture circuit, where his cautionary tales have awakened thousands to the horrors of illiteracy—while offering them at the same time all the chills and thrills of hearing a man with one leg tell how he climbed Mount Everest.

How did Corcoran fool all of the people all of the time? At first he didn't. His elementary-school teachers in various towns in the Southwest knew he couldn't read. But instead of testing him for a learning disability, they just figured he was lazy, rebellious or stupid and passed him along to the next grade. Perhaps if he had stayed in one school long enough, a teacher might have found a way to help him. But his family moved too often: In 12 years John attended 17 schools.

His parents were equally undiscering. "John, where was I?" his mother, Agnes, asked in stricken amazement when the oldest of her six children at last unloaded his burden. "Raising five other kids, Ma," he replied gently. And why didn't his father, John, a high school business teacher, sense the problem? Possibly because he was too busy moving from town to town in search of a better job.

Cheating helped Corcoran slither through high school in Blythe, Calif., and the University of Texas at El Paso. He often signed up for too many classes, then dropped those requiring too much writing. He persuaded his girlfriends to write compositions for him, and during exams arranged to sit beside good students and laboriously copy their work.

When he couldn't cheat, Corcoran sweated blood. In college it took him five days of drudgery to memorize the letters that stand for the 96 chemical elements, and after passing the test he cried himself to sleep. "There was no way," he remembers thinking, "that I was ever going to get out of this." But he did. "I learned from radio, TV, film. I picked people's brains. People were my library."

The pressure eased in graduate school, where oral and take-home exams were common. Corcoran won four National Science Foundation grants and pulled an A in sociology at the University of Santa Clara. But when he decided to teach ("After all I'd been through, I really felt I had something to offer my students"), he had to conjure up a whole new bag of tricks. Bookkeeping classes were no problem—he was a whiz with numbers—but when he taught social studies, he assigned no written homework, gave no written tests and never used the blackboard. Pupils chose up sides and debated the subject—in effect, they taught themselves. Corcoran brought in outside speakers. His classes churned with energy and surprises, and students loved them. "A lot of good learning took place," says his former principal. "John was a very good teacher."

Business confronted Corcoran with another set of challenges. In his checkbook he kept a list of spelled-out numbers, and he always asked the people he paid to fill in their own names. No big deal having lunch with a client: He just waved the menu aside and asked for whatever popped into his head. But what about the dozens of letters, memos and contracts that crossed his desk every day? Corcoran developed preemptive strategies: "You read it," he would tell his secretary. "I left my glasses at home." Or: "I'm too busy. Give me a summary." With a sigh, he says, "I had a hundred excuses."

As for contracts, he brought them home to be vetted by his wife, and he took her along when he had to sign papers at the bank. Kathy was the only living soul who knew his secret. He had confessed it to her before they were married, but she hadn't believed him. "I thought he meant he didn't read well," she says. For several years she avoided the issue. Then one day she heard him pretending to read a nursery tale to his baby daughter. In fact, he was simply making up a story that fit the pictures. "My God!" she realized. "He really can't read."

Kathy now admits that living with an illiterate can be almost as stressful as being one. "We got into arguments over me having to write things. But when I said, 'Look it up!' his eyes were like he wanted to kill me, because he didn't even know the first letter." Why didn't she teach him to read? "I sensed that it was something he didn't want to deal with, that I would only be adding to his fear and frustration."

Decades of fear and frustration cut deep scars in Corcoran's basic good nature. "He became an angry, fearful man," Kathy says. "Fearful of being exposed, of feeling dumb and unworthy." Corcoran agrees: "I acted angry, but I really felt frightened and ashamed. If you came close to me, you came close to my secret and you were a danger, even if your intentions were friendly." As a result, the Corcorans made few friends. They had their children, Colleen, 22, and John, 19, and they had each other. But there were times when they were terribly lonely in their palace by the sea.

It took a severe shock—the collapse of his business when the California building boom went bust in 1982—to persuade Corcoran to face his problem. Stripped of the staff that had served as his word processor, he felt "like a quarterback without blockers or receivers," he says. So after rescuing his business, he took steps to rescue himself—wary steps. Still fearful that neither the public nor the banks would support any business run by an illiterate, he withheld the name of his company from Lynda Jones, director of the regional adult learning program.

"It was so hard," Corcoran says of their first meeting. "I don't even know how the words came out. But I said, 'I can't read at all.' " To test the accuracy of this claim, Jones asked Corcoran to write a few sentences stating what he hoped to gain from the literacy program. "It was awful," he says. "Trying to do something children can do, and failing." In frustration he clutched his pencil like a knife and began stabbing the page.

Jones put Corcoran in touch with a volunteer tutor named Eleanor Condit, and the two of them hit it off from the first. "I was like a little boy talking to his third-grade teacher," he recalls, his eyes misting with emotion. "He was so eager," says Condit. "I sensed that here was a man with unlimited ability. But the tools had never been there." They met twice a week in a local fire-house, and Corcoran spent 40 to 60 hours a week doing homework.

"The first 30 days," Corcoran says, "it was touch and go. I couldn't make connections. But suddenly a bell rang—BING!" Words emerged where there had only been infuriating squiggles. "So that's how you look!" Corcoran found himself murmuring. Words were no longer his enemies. The whole world became a friendlier place—and Corcoran a friendlier man. "A healing has gone on in him that is just incredible," says Kathy.

What's more, Corcoran's fears of a public backlash have proved groundless. Business is booming and associates are warmly supportive. Some say he is living proof that literacy is overrated. But to that he gives an unanswerable answer: "Who would want one eye when he can have two?"

—Brad Darrach, and Dianna Waggoner in Oceanside