BALTIMORE, OCT. 1 -- A 640-pound businessman sued the city today, claiming it unconstitutionally refuses to recognize his obesity as a disability entitling him to preferred status in bidding on city contracts.

"They tell me I can't qualify because I'm not black and I'm not a woman," said Donald E. Keister, 30, in front of Baltimore Circuit Court, where he filed the lawsuit. City law discriminates against people handicapped by obesity and needs to be changed, he said.

Keister, who owns a lead paint testing and removal business, said he relies on city business but often loses contracts because of his limited ability to inspect potential work sites and submit bids.

"I can't go on job sites; I can't walk through a 500-unit apartment building," said the 6-foot-7 Keister, who suffers morbid obesity, a chronic condition that makes it nearly impossible to lose weight. He said he also has an enlarged heart and has hypertension, asthma and diabetes.

Keister's 25-page lawsuit asks the court to order the city to grant him minority business enterprise certification, which would entitle him to bid on special set-aside contracts for minority and women contractors.

Under Baltimore law, 15 to 25 percent of city contracts are available, or "set aside," exclusively for women and minorities. The District of Columbia has a similar law.

Keister has been granted minority status by the Maryland state Office of Minority Affairs and by several counties including Montgomery and Prince George's. But Baltimore has consistently barred him, he said.

There's a reason for that, said Neal M. Janey, Baltimore's chief lawyer. The city's set-aside program, he said in an interview, is part of an affirmative action law enacted to correct past discrimination against racial and other minorities and women. The law does not address the issue of handicaps or disabilities, he said.

Janey said a letter by Keister complaining of his situation has been forwarded to an affirmative action task force studying the city law in light of recent Supreme Court rulings.

The task force may recommend hearings by the Baltimore City Council, which ultimately could amend the law to include disabled contractors in the set-aside program, Janey said, but only if there is evidence of past discrimination against the disabled.

For state contracts, the Maryland set-aside program is available to any person suffering a physical impairment that permanently limits "major life activities, such as caring for oneself, performing manual tasks, walking, seeing, hearing, speaking, breathing {or} learning."

Keister, who has operated his own business since he was 17, has six employees, including office staff and field supervisors. He hires additional workers, he said, to do paint removal at older buildings in the city where lead-based paint was used.

Keister estimates his weight at 640 pounds, the amount he weighed last spring when he had his last physical examination. Because of his size, he said, he is weighed on a laundry scale at a local hospital and records his weight only once a year.

He said other members of his family are in the normal weight range. "I was just a weird baby," he said.