Three men were slain yesterday in the District, and another was killed late Saturday. Their deaths raise the number of homicides this year to 214, police said, almost 20 more than were recorded in 1986.

Twenty-four people have been fatally shot or stabbed in the District in the past 30 days, according to police statistics.

An unidentified teen-ager was found lying dead in an alley between the 100 blocks of Danbury and Darrington streets SW about 10:30 last night. Police said they had no motives or suspects in the slaying, but it appeared the youth had been shot in the head.

Neighbors, who said they heard five shots, said the alley served as a nightly trading market for drugs. "We see kids coming in and out of there all the time, making their deals," said one man, who declined to give his name.

Three hours earlier, 35-year-old Hubert Miller of the 3800 block of 9th St. SE, was fatally shot in the chest as he stood in the doorway of his home.

Police said Miller apparently had been involved in a fight with another man, but they would not say whether they had any suspects in the case.

Yesterday morning, in the second stabbing in the District in less than 24 hours, police found a 23-year-old Southeast man lying dead in a grassy area in the 500 block of 14th Street SE.

The man, Michael Sumpter, of the 3500 block of Stanton Road, had been stabbed in the neck and chest. Police said they have no suspects or motives in the case.

About 8 p.m. Saturday night, an unidentified 40-year-old man was fatally stabbed in the 1300 block of W St. NW after arguing with another man.