James W. Seiler, 65, a pioneer in broadcast audience research and the founder of the Arbitron media ratings research system and Media Statistics Inc., died of cancer Saturday at Montgomery General Hospital. He lived in Silver Spring.

In 1949, Mr. Seiler founded the American Research Bureau in Washington, an organization which compiled diaries kept by radio listeners and television viewers in their homes. With these results, broadcasters and advertisers could measure their audiences more accurately.

Prior to the diaries, telephone surveys, personal interviews and Neilsen's electronic meter made up the whole of broadcast audience research methods. Diaries had a twofold advantage over the electronic meter: they provided the demographic statistics of a broadcast audience, and they monitored the new car-radio listening audience. Mr. Seiler's American Research Bureau, which later became the Arbitron Company, was sold in the 1960s to CEIR, Inc., and is now owned by Control Data Corporation.

In 1964, Mr. Seiler founded Media Statistics Inc. in Silver Spring, an organization designed to supplement the findings of the diary method. Whereas Arbitron publishes a quarterly report, Media Statistics issues a monthly report compiled from telephone surveys. The monthly report offers the advantage of being more timely. These reports not only measure an audience but provide background for broadcast license renewal and assignment purposes.

The American Research Bureau began in 1949 with Mr. Seiler and his wife working in a one-room office in the National Press Building. The first year's billings were $40,000. In 1955, billings had jumped to an annual rate of $1.2 million. Under CEIR, in 1962, ARB's gross revenues were about $3 million.

Mr. Seiler and several associates opened Media Statistics in 1964. The company now produces reports in over 200 markets across the country. Today Media Statistics is a leader in the research and study of cable television and video cassette markets.

Mr. Seiler was born in Evansville, Ind., and moved to Washington as a teen-ager. He was a graduate of the old Western High School and a 1939 graduate of George Washington University. During his college days, he worked for station WRC, where he first tested his diary research methods. He served with the Navy in Central and South America during World War II.

After the war, he returned to Washington and WRC. He was research director for the station in 1949 when he left to establish his American Research Bureau.

Survivors include his wife, Mary Glaze Seiler of Silver Spring; a sister, Jean Baldwin of Wilmington, Del., and a brother, William of Springfield.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society, to the Boy Scouts of America, or to a charity of one's choice.