An 11-year-old boy was charged yesterday with selling PCP to an undercover police officer in a District neighborhood, an arrest that highlights the growing number of adolescents involved in the drug trade, according to law enforcement officials.

Sources said yesterday that the boy was arrested Monday in Southeast Washington and presented yesterday in D.C. Superior Court, and that he may be one of the youngest juveniles charged in a District court with drug distribution.

In addition, a police spokesman said police are investigating whether the boy may have been selling the PCP for an adult, an increasingly common tactic used by adult dealers to insulate themselves from prosecution.

"I think that you are finding . . . that it has become more and more common in the street for adult pushers to use juveniles" to sell their drugs, said Judge Ricardo Urbina, the presiding judge of the District's family division.

According to police, the boy was arrested Monday afternoon after he approached an undercover officer in the 300 block of Ridge Road SE and sold the officer a $10 packet of marijuana sprayed with PCP, or phencyclidine.

The undercover officer was responding to complaints about increased drug trafficking in the neighborhood.

The boy was released yesterday pending his next court hearing. No other drugs were found in his possession.

Law enforcement officials said yesterday that the number of juveniles charged in court with selling a drug other than marijuana has more than quadrupled in the last few years, from 119 in 1983 to 514 in 1985.

Police statistics show that the youngest childen arrested last year on drug offenses were three 11-year-olds, but a police official could not say whether those children were arrested for allegedly selling drugs or whether they were ever charged in court.

"We are seeing a tendency towards younger and younger people becoming involved both as couriers and dealers," said Lt. Robert Poggi of the police department's morals division.

"There is a feeling the juvenile is going to be able to avoid serious prosecution because of his age," a police official said, noting that many times the dealers have previous arrests that could affect their prison sentences if they are convicted.

This official said that in most instances the adult dealer will allow the child to hold enough drugs for only one sale, and that after the sale the child passes back the money to the dealer and then is given a new supply.