The incidence and clinical and laboratory features, as well as the structural alterations, of anicteric hepatitis are not established. Evidence for its existence is based on sporadic cases occurring simultaneously with icteric viral hepatitis in circumscribed outbreaks. As a result of a mass serum enzyme survey originally designed to detect pre-icteric cases of viral hepatitis in an endemic population, 32 cases were uncovered on the basis of significantly abnormal serum activities of glutamic pyruvic transaminase (SGPT). These cases were hospitalized for intensive clinical, laboratory, and histopathologic study. The present report summarizes the clinical and laboratory findings in this series of patients. Their pathologic findings, described in the following paper,1 serve in addition to indicate that this group of patients represented a disease entity of chronic, active hepatitis. Materials and Methods SGPT activity was determined in 1,906 soldiers of the Republic of Korea Army, who had recently passed a physical