W. Herbert Brown, 66, a retired economist for the Department of Agriculture, died of cancer Wednesday at Fairfax Hospital.

Mr. Brown, who lived in Fairfax, joined Agriculture more than 30 years ago. He was assigned to the policy analysis group of the Commodities Economic Division when he retired earlier this year.

He was born in Loudoun County, Va. and earned a bachelor's degree from The Pennsylvania State University, a master's degree from the University of Connecticut and a doctorate in agricultural economics from Harvard University.

Mr. Brown received a number of merit awards from the agriculture Department.

He was a lifelong member of the Religious Society of Friends and a founder of the Langley Hill Friends Meeting in McLean, where he also served as a clerk of the meeting.

His first wife, Doris E. Brown, died in 1975.

Survivors include his wife, Jane L., of the home in Fairfax; three daughters, Gertrude B. Rogers of Gaithersburg, Marianna B. Diggs of Washington, and Dorothy B. McDowell of Elverson, Pa.; a son, Walter A., of Washington; three stepsons, William Legge of Grand Junction, Colo., Robert Legge of Etlan, Va., and Christopher Legge of Fairfax; three brothers, Howard, of Lincoln, Va., Edward, of Purcellville, Va., and Samuel, of Hamilton, Va., and six grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society or to the Langley Hill Friends Meeting in McLean.