Lucie Breyer Kay, 67, an economist who worked for the government in the 1940s and with Robert Nathan Associates in the 1960s and who was active in civic groups in Falls Church, died of multiple sclerosis Wednesday at Northern Virginia Doctors Hospital in Arlington.

Mrs. Kay came to Washington in 1939, working for a short time for the Commerce Department. She then spent four years with the U.S. Employment Service and resigned from the government in 1944.

She was an economic consultant with Robert Nathan Associates, a private consulting firm in Washington, from 1962 to 1969. She worked on projects that helped establish area and regional economic and ecological government organizations. She also carried out studies on the effectiveness of government anti-poverty agencies.

Mrs. Kay had lived in Falls Church since 1943. She was a founder of the nonpartisan Citizens for a Better City (CBC) and helped organize the Falls Church League of Women Voters. She testified before the Falls Church City Council on school and city planning matters.

Mrs. Kay, who was born in Nashville, Tenn., was a 1935 graduate of Vanderbilt University there. She earned a master's degree in economics at Columbia University in 1942.

Survivors include her husband of 39 years, Albert Kay, of Falls Church; a son, Jeffrey, of Washington; a daughter, Carol Kay of Amherst, Mass.; a sister, Rose B. Martin of Nashville; three brothers, William R. Breyer of Arlington, J. Breyer Jr. of St. Louis, Mo., and Bernard Breyer of Auburn, Ala., and one grandchild.

The family suggests that expressions of sympathy be in the form of contributions to the Multiple Sclerosis Society for purposes of research.