The District's director of emergency medical services has abruptly decided to retire, citing differences with Acting Fire Chief Adrian H. Thompson over ways to improve response time and overhaul the struggling ambulance bureau.

Acting Deputy Chief Stephen M. Reid, a 25-year department veteran, inherited an array of problems -- including long-standing complaints about ambulance response times and a chronic shortage of paramedics -- when Thompson appointed him last summer. Reid eventually submitted a budget request that warned that the ambulance service was "grossly inadequate" and would require $11 million to fix.

Reid said he turned in his retirement papers March 7 and plans to leave next month. In an interview, he said "differences in policy" spurred his retirement, but he declined to elaborate. Members of the department said Reid had become frustrated as he tried to push for faster, more radical changes.

"It should be a message to those who look at EMS and say, 'Why haven't you done anything? Why haven't you achieved the mayor's benchmarks?' " said Kenneth Lyons, who heads the union that represents paramedics and emergency medical technicians. "I just don't think that this chief [Thompson] has the grasp of the enormity of the problem that Chief Reid had."

Thompson said yesterday that he is committed to improving emergency medical services but wants to take a less costly and more gradual approach. Instead of adding 14 ambulances, as Reid had suggested, Thompson said he plans to focus first on filling staff shortages.

"If you can't staff up as it is, why am I going to buy the other units when I don't have people to ride them?" Thompson said. About 50 of the department's roughly 200 paramedic positions are vacant, as are about 20 of 140 EMT positions.

Along with the staffing problems, the city faces rising demand for help. Statistics from the Fire and Emergency Medical Services Department show that the number of fire calls has held fairly steady over the years, but the number of calls for medical aid has grown. Since Oct. 1, officials said, the city has answered more than 42,900 medical calls and about 12,000 fire calls. Emergency medical workers have complained that they are overworked and at risk of becoming burned out. Meanwhile, ambulance response times have grown worse.

In 1989, the fire department was criticized after a city audit showed that ambulances responded within eight minutes only 49 percent of the time. Now, that standard is met only 33 percent of the time, and the average response time for critical incidents is nearly 11 minutes. The American Heart Association says that heart attack victims should get help within three to five minutes and that their chances of survival decrease by 7 to 10 percent for every minute they wait.

Reid has contended that response times remained slow because the city does not have enough ambulances. He submitted a plan to create dozens of paramedic and EMT positions and add 14 ambulances to the city's fleet of 29. "Our current levels of providing patient care do not meet the demand of service to the citizens of the District of Columbia; they are grossly inadequate," Reid wrote in his budget request last fall.

But in a statement submitted for his confirmation hearing before the D.C. Council last month, Thompson did not mention Reid or his plan. Instead, the acting chief said he wants to counter the shortage of paramedics by hiring "intermediate" EMTs, who can do some of the advanced procedures that paramedics do but have less training and are easier to hire.

Over the long term, Thompson said, he wants to combine the firefighting and medical functions so every employee has equal pay and benefits and the training to work on either firetrucks or ambulances. But the idea has been on the drawing board for years, never fully implemented because of its cost, estimated at $30 million to $70 million.

Thompson appears on the verge of confirmation by the D.C. Council, and a vote could come as soon as Tuesday. Officials said they have not decided on Reid's replacement.

Anne Mohnkern Renshaw, an advisory neighborhood commissioner from Chevy Chase, said she was disappointed that Reid is leaving. "Steve Reid clearly saw what needed to be done in the city to bring the emergency medical services up to speed," Renshaw said.