William Everett Triplett, 55, an attorney adviser with the Interstate Commerce Commission, died yesterday at Sibley Memorial Hospital. He had a heart ailment.

He had served with the ICC for about 23 years.

Mr. Triplett was born in Tulsa, Okla. He grew up in Alexandria, where he graduated from George Washington High School. He also attended Fisbourne Military Academy at Waynesboro, Va.

He was a student at Washington and Lee University in Lexington, Va., when he entered the U.S. Army Air Corps in World War II.

After the war, he earned a degree in foreign service from Georgetown University and a law degree from George Washington University.

Mr. Triplett was immediate past president of the Fairfax County Historical Society. He belonged to the Society of the Cincinnati in the State of Virginia, the National Society of Descendants of the Lords of the Maryland Manors and the Farmington Country Club in Charlottesville. He was a member of Christ Episcopal Church in Georgetown.

He is survived by his wife, Mary Ann, of the home in McLean, and a sister, Virginia Linthicum, of Church Creek, Md.

The family suggests that expressions of sympathy be in the form of contributions to the Heart Association.