The color-splashed cartoon couture of French fashion sensation Christian Lacroix may be fine for playful Parisiennes, but what's a working woman to do? Impress a client by turning up in a bustle? Show up for a board meeting wearing a froufrou? Cut to New York and designer Mary Ann Restivo, 47, who is emerging from the rag trade as the savior of the stylish but sane professional woman.

Susan Saint James, Gloria Steinem and Good Morning America's Joan Lunden all are attracted to the designer's sleek, sophisticated look, and they are not alone. This year Mary Ann Restivo has already done $17 million worth of business, and last month she launched a line of sporty dresses that sell for up to $500. Pouf-lovers may leave their charge cards at home. "Hers is not a way-out collection," says Kal Ruttenstein, a Bloomingdale's vice-president. "Restivo clothes are wearable, with just enough fashion news for shoppers who work."

Restivo has made her reputation by using fine fabrics, such as satin gabardine and wool crepe, plus a deft cut ("We believe in clothes that enhance the body, not overwhelm it") in the service of an understated, elegant look. "You are wearing tailored, pretty clothes without breaking the bank," says Saint James, who owns about 30 Restivos and has added some to her Kate & Allie wardrobe. Steinem agrees. "I felt they were instant classics," she says. "The kind of clothes that after you've died another woman would find in a thrift shop and like."

The New Jersey-born Restivo was warned early on about entering the design game by her father, Joseph, a designer and clothing-store owner until his death in 1980. "I'm not a tough, tough person," she says, "and this business is very, very hard." But father didn't know best. Designing was in the family's genes, dating back to the turn of the century, when Mary Ann's maternal grandfather made shoes in Italy. Joseph went on to create tailored coats and dresses before opening a quality boutique in Vilsburg, N.J., which he named for Mary Ann, the eldest of his four daughters.

"Joseph was a perfectionist with a high-quality taste level, and he instilled a lot of that in Mary Ann," says Bert Reifer, Restivo's business partner since 1980. Family lore has it that by the time she was 2, Mary Ann was already drawing little people in outfits. At 4, she was tagging along with her father on buying trips to Manhattan, and by the time she was 8 the fashion fever had got her. "I was in the back room of a design house," Mary Ann recalls. "There was a tiny mannequin draped in chiffon. I had this sense that I belonged in this room. I said, 'Oh, this is wonderful! I would love to do this.' "

Eventually she enrolled at a Catholic college in New Jersey and studied home economics. But her heart was still in design, and in 1960 she transferred to Manhattan's prestigious Fashion Institute of Technology. After a succession of postgraduate jobs, she landed at Something Special, a junior sportswear company, where she began attracting attention for her kicky, youthful minis and maxis. In 1974 she was hired as a designer for Christian Dior blouses, and by 1980 her own Restivo label appeared on a line of sportswear manufactured by Cisco Casuals. Unfortunately, that was also the year Cisco chose to get out of the women's clothing field; Restivo was given just three months to find other backers.

"It was probably one of the worst years of my life," she remembers. "My father had just died, and I felt, 'My God, I'm going to lose this.' Everything was sort of disintegrating." By 1981, though, she came up with $165,000 in backing and managed to start her own firm. "We built the company surely and slowly," she says. "And we always showed a profit."

Restivo's sanctuary from the frenzy of the garment district and the 12-hour days she puts in at her cluttered office on Seventh Avenue is an elegant one-bedroom apartment near Manhattan's fashionable Beekman Place, where she lives with her husband, Saul Rosen, an associate director of the International Ladies' Garment Workers' Union. Professionally, expansion is in the offing, and in the next two years Restivo hopes to branch out into furs, lingerie, shoes and accessories. It is a prospect that fills her with pride—and with a determination to do even better. "It's a very tough industry," she says, "and nobody thought I could do this. Now I'm the overnight success after 20-odd years. But I've had a lot of struggles to get to this point, and I don't feel I can sit back and say, 'I've made it.' "