The indictment in Florida in late August of Drug Enforcement Administration supervisor Jeffrey I. Scharlatt on four criminal counts, including allegedly smuggling marijuana, made no great splash in the national press. But in the novelistic cops-and-robbers world of the Florida drug trade it was an event of major importance.

Scharlatt, 41, with 16 years' experience as a federal drug agent, was not just any supervisor. A year earlier he had helped direct an undercover DEA operation code-named "Grouper" that led to 155 indictments and an amazing 125 convictions.

It was the biggest "sting" operation in the drug agency's history, and a good part of the credit for its success was given to Scharlatt's handling of Fred Barber, a smuggler who, beginning in early 1981, served as a confidential DEA informer in Grouper, reporting on incoming drug shipments.

Now a first-rank law enforcement officer stood accused of the very crime against which he was supposed to be guarding.

Scharlatt has pleaded not guilty to the charges and has maintained his innocence to his colleagues. But his indictment sent a chill through the DEA, because it was a vivid reminder of what has become one of the most difficult problems in prosecuting the war on drugs: corruption among the law enforcement officials involved.

The breadth of drug corruption has been emphasized by FBI Director William H. Webster, who said at the unveiling of President Reagan's expanded drug enforcement program that "corrupt public officials were absolutely necessary to the success of those enterprises" where such individuals serve as "facilitators or provide an early warning system."

Webster said such efforts were succeeeding "because of the large amounts of cash" that were available. To make his point, Webster listed several cases over the last year:

In Henry County, Ga., the sheriff, chief of police and others were convicted of aiding smugglers in a safe landing at an airport and "providing an escort service" into Atlanta.

In June of this year, 10 officers of the Chicago police force were convicted of taking payoffs from narcotics dealers.

In Miami, six detectives of the Dade County police department were convicted of accepting bribes and aiding drug traffickers.

Webster did not limit his list to local police officials.

He admitted that there were "problems with agents of DEA, agents of the FBI and prosecutors within the Department of Justice" that were under investigation and predicted ominously that "we expect indictments within the near future."

The court records on the Scharlatt case provide an inside look at how those investigations may have begun and may be run.

When the possibility arose that Scharlatt's activities needed investigation, the DEA, under new supervision by the FBI, went at it with a vengeance. "We love to hang crooked cops," one experienced DEA official said, "in part out of self-protection."

It is typical of the bizarre drug business world that Scharlatt's informer on other smugglers, Barber, became the DEA's chief informer on him.

Not surprisingly, Scharlatt knew that possibility existed. While the DEA investigation of him was under way, Scharlatt met several times with Barber, not knowing the latter was recording their sessions for the DEA, according to court records.

The first suspicion that something unusual might be going on in the Scharlatt-Barber working relationship came last March 8, according to DEA officials, when a small plane landed in Palm Beach County. Scharlatt and another agent watched it land and as it came to a halt, Scharlatt told his colleague that there was no need to inspect it for drugs. According to the DEA source, Scharlatt said that he had arranged this plane flight into Florida just to test the capabilities of Vice President Bush's joint task force that was put together to cut into the flow of marijuana and cocaine coming into south Florida from the Caribbean and South America.

After Scharlatt and his colleague left the field, however, according to DEA sources, a van pulled up and unloaded bales of marijuana from the plane. The shipment was discovered, however, when suspicious local police authorities stopped the van and found the illegal marijuana.

When Scharlatt's companion found out that drugs had been on the plane, he filed a report with the internal security division of the DEA and an investigation was begun.

That inquiry led to the discovery on March 25 of 1.8 million Quaalude pills, worth $1 million at wholesale prices, in the airplane hangar behind Barber's home.

Barber was arrested and, faced with the prospect of a conviction, began talking about Scharlatt, according to DEA sources. Among the things Barber said took place before March 25, according to testimony during the Aug. 27 bail hearing by a DEA agent, was a payment to Scharlatt from Barber of $50,000.

On April 2, DEA officials signed a four-page agreement with Barber, according to federal court records here.

The "contract," as described by Assistant U.S. Attorney Carolyn Heck during the bail hearing, said criminal charges against Barber for possessing the $1 million worth of Quaalude pills would be dismissed if Barber gave his "candid and truthful cooperation" to the agency's internal investigation of Scharlatt.

Dozens of DEA agents were turned loose to look into Scharlatt's past, and a wiretapping operation was begun. One result, according to papers filed in court, was 18 tape recordings and two volumes of transcripts of telephone conversations and documents.

On Aug. 24, a federal grand jury indicted Scharlatt on four criminal counts, including smuggling marijuana and obstruction of justice by interfering with grand jury questioning of Barber.

Scharlatt's career up to the point when the Quaaludes were found in Barber's hangar had seemed exemplary. He was a stickler for detail and a hard worker, according to his colleagues. He had joined the old Bureau of Narcotics and Dangerous Drugs of the Justice Department in 1966, and continued on through the agency's many changes.

In 1980, he moved his wife and two children to Florida, where he had become a group supervisor and leading figure for the DEA's Operation Grouper.

"He made terrific cases," was one agent's description of Scharlatt in those days.

However, there was another side of Scharlatt's life.

At the bail hearing, the government lawyers said Scharlatt owned a $20,239 Cadillac, which he had purchased on time, and until July of this year, a $17,000 Corvette.