BUENOS AIRES -- As Argentina's military struggles with the transition from dictatorship to democracy, the police department of downtown Buenos Aires is winning high marks, even from past critics, for its efforts to adjust.

Under military governments that ruled from 1976 until 1983, police often had a hand in the abduction, torture and murder of suspected subversives. Police tasks went beyond law enforcement to what were described as "political security duties," assigned by the military commanders who ran the departments.

Now, leadership of the municipal forces is back in the hands of career policemen, and a new style of law enforcement is taking hold.

The shift is far from universal. In Greater Buenos Aires, a vast metropolis of 10 million people -- almost a third of the Argentine population -- the downtown Federal District's improved police record contrasts with persistent reports of police atrocities in poorer, more roughneck outlying municipalities. There, the number of civilians killed in confrontations with police continues to exceed substantially the number wounded or detained. Allegations of police brutality and extortion abound.

Much of the credit in the Federal District goes to police veteran Juan Angel Pirker. Since he became police chief a year ago, the number of civilians killed in police actions has dropped dramatically. There have been more investigations of alleged police corruption, and officers have oriented themselves more toward community service than they did in the days of military rule, according to human rights groups, political analysts and other residents.

Street crime is up, and so is drug abuse -- facts variously attributed to the dissolution of the old military order, the adoption of democratic freedoms and the deterioration of the economy. Yet the rule of law is being restored, and its enforcers are themselves learning to abide by it.

Pirker, who has been a policeman since he was 18, represents a new breed of Latin American officials who spent formative years witnessing activities of the repressive regimes of the 1970s, but who have emerged with reputations for probity intact.

At the Center for Legal and Social Studies, human rights activists track police activity reported in the press. "There has been a substantial change in the capital area since the coming of Pirker," said Daniel Frontalini, a worker at the center. "He appears to have changed the methods of control. The number of deaths has dropped from six per month to about four, a decline of 33 percent."

Pirker is reluctant to take credit for the decrease. "I never issued an order to kill fewer people," he said in an interview. "If the number of deaths is down, it's a coincidence or an act of God."

But local experts say that under his command, the image of police officers here has begun to evolve from "military cop" to "citizen cop."

Pirker's most publicized moves have involved crackdowns on corruption, including the jailing of several precinct officers accused of extortion, and investigations into local massage parlors and stolen-car rings linked to retired officers.

Drawing staff from desk jobs and sending them to the streets, he has increased the number of beat police, a move that is part of a plan to give crime prevention higher priority.

Pirker also likes talking to the press, using interviews to emphasize the need to avoid obsessive secrecy in police affairs.

Altering the behavior and mindset of an institution more accustomed to authoritarian regimes than democratic ones is a sensitive task. Pirker's innovations have not been popular with all officers.

Pirker himself cautions that while changes in Argentine society are necessary, they should not come too rapidly.

"We're going through a transition in Argentina," he said. "We're seeing an exaltation of individual rights, which is natural. But if you suddenly take the lid off, everything comes out in a rush and in ways not always respectful of others."

"Pirker would like to do something to change things, but it is very difficult," said Alicia Oliveira, a human rights attorney. "It means going against a whole network, a mafia. Lots of cases exist that he still cannot control."

Oliveira is investigating two such cases, both involving the deaths this year of teen-agers said to have been killed in shootouts with police. She said evidence suggests the youths were murdered because they refused police officers' efforts to use them to steal. One of the youths had filed a statement in court complaining of such efforts shortly before he was found dead.