Forty-five patients with localized non-Hodgkin's lymphoma of unfavorable histologic type (41 patients had diffuse histiocytic, 2 had nodular mixed, and 2 had minimally nodular histiocytic lymphoma) were treated with initial chemotherapy (28 patients), including cyclophosphamide, adriamycin, vincristine, and prednisone (CHOP), or with initial CHOP followed by involved field radiotherapy (17 patients). Patients were clinically staged and found to have stage I (7 patients), stage IE (8), stage II (12), and stage IIE (18). Despite the presence of potentially adverse prognostic factors, including age older than 65 yr (11 patients), bulky disease (17), gastrointestinal involvement (9), and “B” symptoms (4), 44 of 45 patients (98%) achieved a complete response. Forty-two patients (93%) are alive with a median follow-up time of 41 mo (range 3–128 mo). Thirty-eight patients (84%) remain continuously free of disease. Neither the pretreatment clinical features nor the type of treatment significantly influenced the outcome for patients treated with initial chemotherapy. Patients who failed treatment relapsed at distant sites or in initially involved sites whether or not they received radiotherapy. Initial treatment for localized lymphomas of unfavorable histology with chemotherapy regimens of proven curative potential in advanced disease is a successful treatment strategy and obviates the need for extensive staging. The role of involved field radiotherapy following initial chemotherapy needs to be defined.