Leslie Renee Jancar, 22, a lifeling resident of Cabin John and an art student who hoped to become a medical illustrator, was killed early Sunday when the automobile she was driving struck a guard rail on the Capital Beltway near River Road in Bethesda.

Miss Jancar was a 1974 graduate of Walt Whitman High School in Bethesda. She studied art at Montgomery College, from which she graduated in January 1977 and was an art student at George Washington University at the time of her death.

Members of her family said she planned to go to Europe this summer to further her art studied and that she hoped to become a medical illustrator.

In addition to her studies, Miss Jancar had worked as a sales clerk in the Super Giant department store in Rockville for almost five years and had recently been transferred to a Gint Drugstore in Rockville, where she was a secretary. She was a member of a Giant softball team.

She also was a member of the Church of the Little Flower in Bethesda.

Survivors include her parents, Frank James Jancar Jr. and Mary B. Jancar, of the home in Cabin John; a sister, Shelia Dianne St. Calir, of Silver Spring, and a brother, Frank James III, of the home.