Kenneth B. William, 66, a retired adviser with the Federal Reserve Board, died Tuesday at his home in Chevy Chase after an apparent heart attack.

He had joined the board's division of research and statistics in 1941. As chief of the national income, money flows and labor section, he played a key role in analyzing economic developments and in recruiting and training economists.

Mr. William, who retired at the end of 1974, had been a member of the Federal Reserve System's committee on current business developments for many years.

In 1946, his paper, "Employment and Wage Policies," became part of the Federal Reserve's postwar economic series. He was a member of the U.S. delegation to a semiannual meeting of the United Nations Economic and Social Council in Geneva, Switzerland, in 1958.

Born in Brunswick, Maine, Mr. Williams graduated from Stanford University in 1932, and followed that with two years of graduate work there. He later received a master's degree from George Washington University. He taught briefly at George Washington and the Universtiy of California at Los Angeles.

He came to Washington in 1935 to work in the research division of the Works Projects Administration.

Mr. Williams was a fellow and former chairman of the business and economic section of the American Statistical Association.

He was a member of the Conference on Income and Wealth, sponsored by the National Bureau of Economic Research; the National Association of Business Economists and the Business Economists Council. A charter member of the National Economists Club, he had served on its first board of directors.

He is survived by his wife, Jean, of the home; a Randall, of Frederick, Md.; a daughter, Margaret Underwood, of Simsbury, Conn.; a brother, Stanley, of Williamsburg; a sister, Beatrice Curtin, of Vallejo, Calif., and four grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to Children's Hospital.