We studied retrospectively the influence on the prognosis of patients with localized non-Hodgkin's lymphoma of extranodal type with regard to the duration of an anthracycline-based combination chemotherapy-modified CHOP regimen. The patients who were given at least 2 courses of chemotherapy and attained complete remission were selected. These were subdivided into two groups; one for patients who were given 2-6 courses, the other for patients given 7-10 courses. The relapse-free survival curve for patients treated with 7-10 courses was slightly better than that of the patients treated with less than 6 courses. However, the difference between them was not significant. From the results, it was considered possible to reduce the chemotherapy from 10 to 6 courses in patients with localized non-Hodgkin's lymphoma of extranodal type. A prospective randomized study is now in progress at Saitama Cancer Center.