Hassan H. Mohammadi's testimony yesterday that he gave drugs to D.C. Mayor Marion Barry is not the first time he has informed on a friend. Mohammadi's information helped send another government official, an employee of the U.S. Immigration and Naturalization Service, to jail.

The prosecution in the Barry case put the 36-year-old Mohammadi on the stand to testify that the mayor visited the Pardis Cafe, the Georgetown restaurant Mohammadi operated, and Mohammadi's nearby apartment to snort cocaine or pick up drugs for later use.

Mohammadi pleaded guilty May 29 to a single misdemeanor charge, conspiracy to possess cocaine.

The restaurateur testified that he first met Barry in August 1984 at a party held for the D.C. delegation to the Democratic National Convention in San Francisco. He said that when he opened Pardis on M Street NW in February 1985, he invited several people he had met in San Francisco, among them Barry.

Acquaintances say Mohammadi and his family came to Washington from Iran in the 1960s so that Mohammadi's father could take a job as a chef at the Iranian Embassy on Massachusetts Avenue NW.

During the late 1970s, Hassan Mohammadi was a consulate office clerk at the embassy, which was then presided over by Shah Mohammad Reza Pahlavi's urbane ambassador, Ardeshir Zahedi, who flew in Iranian and Soviet caviar and French wines by the crate for some of the most elegant parties in town.

He later worked as a passport officer, fielding 250 to 300 requests a day from Iranians desperate to stay in the United States or get members of their families out of Iran, he stated in a 1982 sworn affidavit.

Mohammadi lasted only a year in that job before he was fired by the new regime of the Ayatollah Ruhollah Khomeini, but by then he had found the revolving door out of government into a high-paying niche in the private sector.

"I opened up a business in which I sold cars and exchanged money," he said in the affidavit. "People who knew me at the embassy continued to come to me for advice . . . . Based upon what I thought would be a lucrative business arrangement and opportunity to help my countrymen, I added immigration consulting to my business."

Mohammadi and several Iranian colleagues drew about 300 wealthy Iranian clients willing to pay them tens of thousands of dollars to get permanent resident status in the United States. Mohammadi and his associates delivered immigration papers to them by bribing an INS official, according to court papers.

"He made a lot of money, lived the high life, going to Las Vegas and losing $70,000 in one night," said an Iranian who knew him well in those days. He said Mohammadi moved to Rockville, bought a Rolls-Royce and began dabbling in real estate.

The good life didn't last long. In September 1982, Mohammadi and five others, including the INS officer, were indicted. Mohammadi quickly agreed to help the government in its prosecution of his confederates and to become an informer in other unrelated investigations.

Mohammadi, who allegedly netted $171,000 in the scheme, was fined and sentenced to four years' probation. In a sentencing report for the court, prosecutors said they found him "one hundred percent cooperative and an effective witness."

In 1985, Mohammadi and his wife, Yasaman Rowhani, opened the Pardis Cafe on M Street in Georgetown, a Persian restaurant that soon converted to more popular Italian fare. He testified yesterday that he is in the process of selling the business.

Along with the restaurant and an upscale town house in Georgetown, Mohammadi was acquiring a string of debts -- to friends, creditors and the IRS.

Barry was interviewed last summer about the relatively unknown collection of people who had become his most intimate friends in recent years. Among them was Mohammadi. Most of those people didn't know one another, and several of them have been named as unindicted co-conspirators in the drug and perjury case against the mayor.

Barry's recollection of how he and Mohammadi met differs slightly from Mohammadi's. Barry said he met him at a social event at the Iranian Embassy in the late 1970s, then lost track of him for several years.

He said he met him again a few years ago at a party given by former Scranton, Pa., mayor Jim McNulty at the Pardis Cafe. Mohammadi and his wife have been to Barry's home since then, said the mayor, and "I've been to his house with five or six people."

Ivan Socher, a former neighbor of Mohammadi's, said he saw Barry arrive several times at Mohammadi's home around 10 or 11 p.m. in the past year. Other acquaintances said they saw Barry at Pardis. Barry and his wife, Effi, appeared in a magazine advertisement for the restaurant two years ago.

Weekend and after-hours phone logs investigators obtained from the mayor's command center show 25 calls from Mohammadi in 1988 and 1989.

Hazel Diane "Rasheeda" Moore has testified that she and Barry used opium and cocaine supplied by Mohammadi on several occasions, at her apartment and in a small office above the Pardis Cafe.

Mohammed Sia Pasikhani, a former drug dealer, told a federal grand jury in Alexandria last year that he regularly supplied Mohammadi with cocaine. According to a transcript of that testimony, Pasikhani said Mohammadi "has gotten some cocaine for the purpose of entertaining some guests."

In 1988, Mohammadi and former Scranton deputy mayor Richard Rossi formed a company called Media Productions Inc., and six months later they won a $195,000 marketing contract from the District lottery board. One of the firm's officers was Bryant Harris, husband of Jeanne Clark Harris, whose marketing firm once employed Effi Barry. Federal authorities have been investigating that contract award.

"Once, he mentioned the lottery contract with Rossi," said a Mohammadi acquaintance who asked not to be identified. "He said they are doing a great job and hope to grow and build on that and get more contracts."

Staff writer Michael York contributed to this report.