Kimura's disease is considered to be a Th2 type allergic reaction based on the presence of eosinophilia and IgE hyperimmunoglobulinemia. We report a 26-year-old Japanese male with this disorder associated with ulcerative colitis. IL-5 is a selective stimulator for the production of eosinophilia and is considered to play an important role in Kimura's disease. IL-5 mRNA from peripheral blood mononuclear cells and the colon lesion were detected by the reverse-transcriptase polymerase chain reaction method, indicating that IL-5 can also be of importance in ulcerative colitis.