Sunday circulation of The Washington Post exceeded 1 million copies for the first time in the newspaper's history during the six month period that ended March 31, the Post reported yesterday.

Sunday circulation in that period averaged 1,005,468, a gain of more than 19,000 copies over the same period a year earlier. The Post became one of six Sunday newspapers with circulations exceeding a million. The others are the New York Times, New York Daily News, Chicago Tribune, Los Angeles Times and Philadelphia Inquirer.

The other newspapers are in larger metropolitan areas than Washington, and Post President Thomas Ferguson said the Post's figure means the paper is being sold to 73 percent of the families in the area, "by far the highest of any big city newspaper in the country."

In the past three years, Post circulation has increased 21 percent on Sunday and 24 percent daily. In the most recent six month period, however, daily circulation declined by more than 13,000 copies, to an average of 747,676. Both the Sunday and daily circulation figures cited by Ferguson for the six month period have been filed with the Audit Bureau of Circulations for certification.

Ferguson said the decline in daily circulation was the result of a deliberate company decision to reduce distribution outside the Washington-Maryland-Virginia area, economic conditions in the recession, and "some impact" from USA Today.