Pamela McDonald, 29, director of development at the Phillips Collection art gallery here, died Wednesday of injuries sustained in a fall from the fourth-floor window of her Washington apartment.

The D.C. Medical Examiner's Office said the circumstances of the death were still under investigation and that toxicological tests were in progress.

Miss McDonald worked in fashion merchandising and as a research manager for an advertising agency in New York City before moving to Washington a year ago.

She was born in Clarks Green, Pa., earned a bachelor's degree from Connecticut College and completed course work for a master's degree in fine arts at the University of Delaware. While working on her master's degree, she was an intern at the Brandywine River Museum in Chadds Ford, Pa.

Miss McDonald was a member of the American Association of Museums and the Connecticut College Club of Washington. Her hobbies included playing squash.

Survivors include her parents, Frank J. Jr. and Margot Williams McDonald, and two sisters, Lynn and Elaine, all of Clarks Green, and a stepbrother, George Rowbottom of New Haven, Conn.

The family suggests that expressions of sympathy be in the form of contributions to a charity of one's choice.