The efficacy of multimodality treatment of gastric lymphoma was examined in a retrospective study of 46 patients treated at the Memorial Sloan-Kettering Cancer Center from 1971 to 1982. The principal treatment plan consisted of surgical resection of the gastric lymphoma (n = 36) where feasible, followed by radiation therapy of the whole abdomen (n = 23) with a boosting dose to the stomach-bed to 3700 cGy, and/or chemotherapy using mainly the CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) regimen as an adjuvant (n = 7), or CHOP plus other drugs for advanced disease. The median follow-up time of patients was 61 months (range, 30 months to 14 years). There was no operative mortality. No patient developed known relapse in the abdomen after resection and total abdominal irradiation, and none suffered relapses after adjuvant chemotherapy, for Stages I-E and II-E. At 5 years, the estimated survival rate after treatment was 95%, 78%, and 25%, respectively for Stages I-E (n = 20), II-E (n = 9) and IV (n = 17). The results for Stage I-E and II-E resectable tumors were significantly improved (P less than 0.05 and less than 0.1 respectively) over those of similar tumors treated in 1949 to 1970.