The pathologic features of Candida albicans and Candida tropicalis in 23 consecutive autopsied patients with culture-proven disseminated candidiasis were studied in order to determine the pathologic basis for the greater virulence of C. tropicalis. Disseminated C. tropicalis infection with gastrointestinal invasion occurred only in eight neutropenic patients; whereas, C. albicans infection occurred in nine neutropenic and six nonneutropenic patients. C. tropicalis involved the entire alimentary tract in four of eight patients versus one of fifteen patients with C. albicans. C. tropicalis penetrated to the deep submucosa in six of eight patients with C. tropicalis and four of fifteen patients with C. albicans. Nine of ten patients with submucosal invasion were neutropenic. Invasion of submucosal blood vessels occurred in six of eight patients with C. tropicalis and only two of fifteen patients with C. albicans. All patients with submucosal blood-vessel invasion were neutropenic. A band of tissue necrosis at the advancing mycelial margin was present with C. tropicalis but not with C. albicans. These autopsy findings indicate that the greater virulence of C. tropicalis is related to increased invasiveness in the gastrointestinal tract in susceptible hosts.