An 88-year-old Northwest Washington woman was found beaten to death last night in a vacant lot in a warehouse area near Fourth and T streets NE, D.C. police reported.

The victim, Evelyn M. Garrett of 2200 19th St. NW, was discovered about 8:30 p.m.--apparently shortly after she was attacked--by a passerby who immediately summoned a fire department ambulance. Paramedics who arrived minutes later tried to revive the woman with cardiopulmonary rescucitation as they rushed her to the Washington Hospital Center, officials said, but she never regained consciousness and was pronounced dead at 10:l5.

Homicide detectives described the slaying as particularly savage and said that robbery was apparently the motive, but declined to give further details on that aspect of the investigation.

Police said Garrett was last seen about 7 p.m. in a shopping area of Northwest, and detectives had not determined last night how she might have gotten to the remote area of Northeast near McKinley High School where she was found. One detective speculated that she may have been attacked elsewhere in the city, then taken to the lot by car and dropped.

Investigators declined to describe the slaying scene or comment on whether a weapon might have been used in the beating. One detecitve said, however, that "It takes somebody who's sick to do something like this."

Police were unable to provide any information about Garrett's background, except to say that it appeared she was a widow who lived alone, and that her closest relative seemed to be a brother in Pennsylvania.