Don Warren, who trained the champion Acclamation and had a California stable for decades, died early Thursday of kidney failure, Santa Anita announced on Friday.
Warren was 67 and had been in declining health in recent years, which led to his retirement from training in the summer of 2015.
"He had been taking pain medication for a degenerative back disease, which caused his kidneys to shut down," Rhonda Schiewe, Warren's sister, told Santa Anita publicity.
Born in Covina, Calif., Warren began working in the stables in 1969 and began working for Old English Rancho as an exercise rider in 1970. Warren began training for Old English Rancho in 1974 and worked for the prominent California farm for the next 40 years, until his retirement.
Warren won his first stakes at Turf Paradise in 1977 and his first six-figure race in the 1984 Valkyr Handicap at Hollywood Park.
Acclamation was by far Warren's finest runner, a winner of 11 of 30 starts and $1,958,048. Acclamation, owned by Old English Rancho, won his last seven starts and won six Grade 1 races, including the 2011 Pacific Classic at Del Mar and consecutive runnings of the Eddie Read Stakes at Del Mar in 2011 and 2012 and three straight runnings of the Grade 1 Charles Whittingham Stakes at Hollywood Park from 2010 to 2012.
Survivors include his wife, Patty, daughters Amanda, Jennifer and Diana, and a brother - the retired jockey Ron Warren, Jr.
Funeral services are pending.