George W. Millias, 51, special assistant to the director of the U.S. Fish and Wildlife Service, died Saturday at Arlington Hospital after a long illness.

He joined the service in 1974 as deputy director and was named special assistant to the director this past July.

From 1973 to 1974, Mr. Millias was director of environmental quality in the Defense Department and chairman of the department's environmental council.

Before coming here he had serve for a year as deputy administrator of the San Francisco region of the Environmental Protection Agency. He was responsible for programs in California, Nevada, Arizona, Hawaii and the U.S. Pacific territories.

Born in Gilroy, Calif., Mr. Millias was a graduate of San Jose State University and received a master's degree from Stanford University.

He was a rancher and hotel manager before becoming a member of the California State Assembly in 1963. He served in the Assembly until 1971 and was chairman of several environmental committees.

He is survived by his wife, Mary Ann, of the home in Alexandria, and his parents, Mr. and Mrs. George C. Millias, and a sister, Carol Silacci, all of Gilroy.

The family suggests that expressions of sympathy may be in the form of contributions to the Cancer Memorial Fund or the Heart Fund.