In a registry of 24,105 cancers, 15 patients were found to have three primary cancers in different organs. Decreasing time intervals between sequential diagnoses and then death were noted. Occurrence and sequence of cancer sites appeared to be random. Stage of second and third cancers tended, on the average, to be more advanced than those of the first cancers. This study strengthened the hypothesis that patients with primary cancers in different organs are victims of compromised host defenses against cancer.