Marcos Cadavid, an accused Colombian drug wholesaler, was paid about $20 million from 1976 to 1981 by members of a Washington-based cocaine distribution ring, a federal prosecutor alleged yesterday in Cadavid's trial at U.S. District Court here.

"Many of those kilograms -- 2.2 pounds of cocaine each -- were brought here and sold here, on the streets of Washington," Assistant U.S. Attorney Roger M. Adelman charged in an opening statement to the jury.

Adelman alleged the drugs were also distributed in Virginia, Texas, New Jersey and California by the ring, whose leader, Lawrence G. Strickland Jr., 34, of Bethesda, has pleaded guilty and is testifying as the government's star witness.

Strickland recounted a drug purchase in Miami in which he showed up carrying a shopping bag containing $350,000 in cash hidden under a few T-shirts. The cash was exchanged, Strickland testified, for 10 kilograms of cocaine from Cadavid and a second Colombian.

Cadavid, who is charged with conspiracy to import and distribute cocaine, was among the first defendants extradited by the Colombian government in January under a new treaty with the United States aimed at cracking down on the drug trade.

The federal courthouse here has been placed under unusually heavy security during the trial following threats from Colombian drug kingpins angered by the extraditions.

Cadavid's lawyer, Melvin Kessler of Miami, charged yesterday that Strickland, who has not been sentenced, "made himself a deal, commonly called a sweetheart deal" with prosecutors to win a reduced sentence in exchange for his testimony against Cadavid.

Strickland, a 1969 graduate of Wilson High School in the District, testified that he was a small-time drug dealer until he met a Miami lawyer in the late 1970s who in turn introduced him to Cadavid and the second Colombian, Armando (The Hammer) Marulanda.

The two Colombians, Strickland testified, permitted him from the beginning to buy cocaine in large amounts on credit. "It was a leap -- a different business almost," he said.

Strickland testified that the credit arrangement with Cadavid and Marulanda enabled him to buy cocaine in 10 kilogram and later 20 kilogram lots, paying in installments with bags or suitcases of cash.

Prosecutor Adelman told the jury that Strickland paid an estimated $8 million to $10 million to the Colombians over a five years, including a single cash payment of $475,000.

Adelman said another prosecution witness, Michael Ribera, an associate of Strickland's in the drug deals, will testify he gave Marulanda and Cadavid an additional $1.5 million in cash to buy cocaine.

"That's dope money Cadavid had in his hands, every bit of it," Adelman said.

The prosecutor said Cadavid and Marulanda displayed 300 kilograms of cocaine to a third prosecution witness, James Kastrenakes, and that Kastrenakes subsequently bought 150 to 175 kilograms for between $8 million and $9 million in cash.

Marulanda, who is a fugitive, eventually retired from the drug trade, according to Adelman, and Cadavid became "Number One . . . the principal supplier" of cocaine to Strickland and his associates.

On cross examination, Kessler asked Strickland whether Marulanda didn't consider Cadavid "a flunky, a gofer?"

"I'm sorry," said Strickland. "He didn't say that at all."