William Grahm Boyce III, a former riding instructor who also bought and sold show horses, died of cancer Monday at St. Mary's Hospital in Leonardtown. He was 63 and lived in White Hall, Baltimore County.

Born in Evanston, Ill., and raised on his grandmother's Glencoe farm, Mr. Boyce attended St. Paul's School and graduated from Hereford High School in 1959.

As a youngster, Mr. Boyce developed an interest in show ponies. During the late 1950s, his pony, Smoky Joe, was a Maryland and U.S. champion.

He went to work in 1959 in the reproduction department at Commercial Credit Corp. in downtown Baltimore. In 1965, he left the company to establish the Bacon Hall Equestrian Center in Glencoe, where he gave riding instruction to young students.

"He had a patient manner with young riders, gave them assurance and developed many champions," said a brother, Thomas T. Boyce of Baltimore.

In addition to giving riding instruction, Mr. Boyce traveled throughout the country and the world buying and selling show ponies.

"In 1980, the deposed shah of Iran offered him a handsome sum to rescue his horses. He turned him down," said Thomas Boyce.

Mr. Boyce enjoyed boating, fishing and spending time at a second home he maintained at Piney Point.

His marriage to Mary Love Grunow ended in divorce.

A memorial service will be held at 11 a.m. July 3 at Immanuel Episcopal Church, 1509 Glencoe Road in Glencoe.

Mr. Boyce is survived by his wife of two years, the former Sandra King Kelly; a son, William Grahm Boyce IV of Sparks; another brother, James Simons Boyce of Quantico, Va.; two stepbrothers, William Roome and Rodney Roome, both of Wolfboro, N.H.; three stepdaughters, Dr. Deborah Kelly of White Hall, Terrie Emanuel of Moshi, Tanzania, and Sandy Lee Bertrand of Nederland, Colo.; and three grandchildren.