Splenomegaly and massive splenomegaly were diagnostically evaluated retrospectively at Stanford University Hospital in 147 patients over 8 years and compared to the nearby county hospital (Santa Clara Valley Medical Center; VMC) in 170 inpatients over 11 years. Hematologic diseases at Stanford (data for VMC in parentheses) occurred in 66% (35%; p < 0.001) of the patients with splenomegaly and in 84% (54%; p < 0.001) of those with massive splenomegaly. Hepatic diseases occurred in 9% (36%; p < 0.001) of the patients with splenomegaly and in 5% (29%; p < 0.001) of those with massive splenomegaly. Splenectomy was performed in 71% of the patients at Stanford and in 9% of those at VMC (p < 0.001). The combined Stanford-VMC series showed significant associations (p < 0.01): for hematologic diseases with massive splenomegaly, lymphadenopathy, and blood cytoses; for hepatic diseases with hepatomegaly, cytopenias as hypersplenism, and abnormal liver function tests, and for infectious diseases with fever.