Ava Diane Poe, 33, deputy clerk of the U.S. Tax Court, died Monday in a two-car automobile accident near San Luis Obispo, Calif.

Miss Poe, of Arlington, and the driver of the vehicle in which she was riding, Mary Ann Russell, of Falls Church, both were pronounced dead at the scene after their care was struck head-on by another car that crossed over into their lane, according to a California Highway Patrol spokesman. They were traveling together on a vacation trip. The accident occurred on a road between U.S. 101 and the Coast Highway.

The four passengers in the other vehicle are in critical condition from burns suffered when their vehicle caught on fire, the highway patrol spokesman said.

Miss Poe, a native of Greenwood, Miss., began working in the office of the chief counsel for the Internal Revenue Service in 1970, after earning a doctorate in law from Southern Methodist University's law school.

She was appointed assistant clerk to the Tax Court in 1975 and promoted to deputy clerk in 1978.

She was a member of the First Baptist Church of Alexandria.

Survivors include her parents, Mr. and Mrs. James F. Poe, and a sister, Sandra Allison, all of Memphis.