Pathologic studies of the liver were performed on 30 autopsied cases of Kawasaki disease. The cases were classified into four groups (stages I-IV), and stage IV was further divided into two subgroups according to the duration of the illness at the time of death. Liver weights were markedly increased in stage II (12-25 days) and in stage III (28-36 days) but returned to normal in stage IVb (7 months to 6 years). Likewise, spleen weights were also markedly increased in stages II and III. Stage I (0-9 days) and stage II were characterized by acute inflammation in portal area, and degree of inflammatory changes decreased gradually. There was significant correlation between hepatomegaly and the degree of inflammation in portal areas, but not with definite heart failure or the use of drugs. These data suggest that the pathogenesis of hepatomegaly in acute-stage Kawasaki disease involves the inflammation in portal areas and/or latent heart failure.