The results of an autopsy of an 80-year-old Japanese male with acute myeloid leukemia who died of spontaneous rupture of the spleen are reported. The patient was admitted because of anorexia, fatigue, weight loss, and multiple skin eruptions. Hematological examinations indicated a rapid increase in myeloblasts. The patient collapsed on the 28th hospital day, immediately after complaining of severe epigastralgia and vomiting. He died ten hours later. The autopsy revealed extensive leukemic infiltration of the bone marrows, spleen, lymph nodes, skin, and other internal organs. The spleen was enlarged and was ruptured in places at the hilar portion. Massive intraperitoneal hemorrhage from the rupture was the direct cause of death. The mechanisms of splenic rupture are discussed.