Since 1982, we have performed 384 courses of CHOP chemotherapy for 89 patients with malignancy including 70 with non-Hodgkin's lymphoma, adhering to the original regimen as strictly as possible. As severe acute reactions, myelosuppression, fever, arrhythmia, hemorrhagic cystitis, and perforation of duodenal ulcer were seen. Rates of fever had no tendency to increase with advancing age. Three patients only with diabetes mellitus had no severe side effects. Three patients with liver cirrhosis showed severe myelosuppression and fever. One patient both with liver cirrhosis and diabetes mellitus died from the infection due to CHOP chemotherapy, however the other febrile patients did not have life threatening infection. Thirty three percent (11/33 courses) of the patients with obesity experienced severe myelosuppression (WBC less than 1,000), while 55% (33/60 courses) of the patients without obesity. However satisfactory treatment results were not obtained in the patients with obesity. We consider that CHOP chemotherapy is excellent in feasibility even for the aged patients or the patients with diabetes mellitus. However, we suggest that the dose of CHOP chemotherapy should be reduced for the patients with liver cirrhosis.