Boston Chicken, a fast food chain with a popular branch in Porter Square, is turning in huge profits this week on the stock market.

Shares of the company's stock, first offered Tuesday morning at $20 per share jumped to nearly $50 by the evening. With a volume of 8.4 million shares, Boston Chicken was the most active issue on the NASDAQ market that day.

The expanding company, founded in Newton, Mass. but now based in Naperville, Ill., was hailed earlier this year as one of the top stock prospects. Tuesday's trading, however, surprised nearly everyone--including the top investors and managers of the relatively small company.

Boston Chicken claims to be leading the fast-food market in restaurants offering rotisserie chicken--a healthier alternative to the fried chicken most other places serve. Investors feel this will help them gain popularity among today's increasingly health-conscious consumers.

Patrons at the Boston Chicken in Porter Square said the restaurant offers some of the best fast food in town.

Suffolk College student Scott Morino said he eats at Boston Chicken at least twice a week. "The food here is healthy--the chicken isn't fried, which makes a big difference," he said.

Lisa Lehr, another patron, was eating at Boston Chicken for the first time in her life yesterday.

"I like it a lot," Lehr said. "It tastes good--and it sure beats McDonald's."

According to a New York Times article, the company's startling market activity Tuesday left many feeling that the value of the stock had been inflated.

"It's a great company, a great management," Brent W. Clum, an analyst at T. Rowe Price, told the New York Times. "But at $48.50, it looks a little rich. I don't understand how it is valued where it is."

Yesterday Boston Chicken dropped back down to $42 per share.

At the beginning of 1993, Boston Chicken's annual revenues were calculated to be $8.3 million. In less than a year, they have opened an additional 85 franchises and their revenue stands at $28.2 million.