After a 15-year decline, sales of suits and ties are on the rise, according to the Doneger Group, a fashion consulting firm.

Investment bankers, analysts and lawyers are hoping professional attire will boost their credibility, which has fallen with the stock market and the dot-com implosion. And job seekers hope that donning suits will give them an edge during interviews in a job market plagued by waves of layoffs.

Frank Quattrone's elite group of tech stock analysts at Credit Suisse First Boston recently were told to dress sharp. "Effective immediately, suit and tie are recommended for group functions and especially if you are meeting a client for the first time. Business casual may pass with clients that analysts know well, however, business casual should still include a blazer/jacket," said a recent e-mail to analysts. Even on the West Coast, where the rules are more relaxed, jackets are required for business casual.

Andrew Kozinn, president of Saint Laurie Merchant Tailors, said sales at his Park Avenue store are up 10% this month, and he expects even better business in the coming months. One of his customers, Stephan Grossnickle, recently went back to wearing suits after a 4-year hiatus. "I just thought, I'm not going to do this any more," says Grossnickle, a managing director for Royal Bank of Canada Dominion Securities in New York.

Wall Street banks and law firms adopted business casual dress in the mid-1990s to pitch Internet entrepreneurs and to lure college graduates who were flocking to then-booming dot-coms.  "It became a big recruiting issue, trying to get people out of schools," says Tancred Schiavoni, a lawyer at O'Melveny & Myers in New York.  But with the turnaround in dot-coms, "Jobs are more competitive, and that's reflected in the dress," Grossnickle says.

Business casual also had some unintended consequences. O'Melveny & Myers had to send out several memos, including one on tank tops, to emphasize the importance of "business" in business casual.