MIAMI (AP) _ A self-described hit man testified Wednesday that he killed 13 people in a career tied to organized crime families, which reportedly control the heroin trade in the United States.

Luigi Ronsisvalle, speaking before the President's Commission on Organized Crime, also said he carried several hundred kilograms of heroin during trips between such cities as Los Angeles, Chicago, Miami and New York.

The commission, which has powers to subpoena witnesses, find them in contempt if they refuse to appear before the panel, and grant immunity from prosecution to cooperative individuals, was holding its fifth public hearing on organized crime in the United States.

Ronsisvalle, 44, said he was born in Sicily and moved to the United States in 1966 when he was 25.

He said he ''knew almost nothing'' of La Cosa Nostra, an American organized crime group, when he arrived in this country. He said he was introduced to organized crime by mentioning the name of a Sicilian friend to Italians in the New York City borough of Brooklyn.

As a result, Ronsisvalle said, he became involved in organized crime and eventually committed 13 murders, including 11 under contract to the Cosa Nostra.

He was convicted for one murder, the 1976 killing of a man Ronsisvalle said had raped his own niece. He was also convicted of threatening a witness in another case. In 1976, he surrendered and agreed to testify.

Ronsisvalle said that while he was growing up in Sicily, he always wanted to be ''a man of honor'' - a member of the Mafia.

He said that in Sicily, people who felt they had been wronged preferred to go to the Mafia for justice because the law took too long and did not mete out severe enough punishment.

''If a man wrongs another man'' the courts could jail him for five years, but ''in Mafia justice you shoot him in the head,'' he said.

Italian organized crime families in the United States are not part of the Mafia and do not provide a system of justice for their members, Ronsisvalle said.

''La Cosa Nostra is something American,'' he told the panel. ''In Sicily you could whistle and in two minutes, you'd have 200 guys behind you with a shotgun.''

In other testimony, John Lawn, who has been nominated to head the federal Drug Enforcement Administration, said that approximately 500,000 Americans use heroin, a number that has remained relatively constant over the last few years. He said nearly 600 people die heroin-related deaths each year in the United States.

Most of the heroin came from Asia, Lawn testified.

During Wednesday's hearing, investigators for the Italian and U.S. governments described connections between heroin suppliers and exporters in Sicily, and Italian-born importers and distributors in the United States.

One witness, Antonio Gambino, a reputed member of the Gambino organized crime family of New York, was brought from jail, where he is serving time on a heroin-trafficking conviction.

Gambino responded ''Fifth Amendment'' to each question posed to him.