The early metabolic events in 33 patients with non-Hodgkin lymphoma were analyzed in the present study. Twenty-three patients had Burkitt lymphoma, 3 had non-Burkitt undifferentiated lymphoma and 7 had lymphoblastic lymphoma. Eight patients developed azotemia prior to starting chemotherapy while five did so during the first treatment week. All the patients but two who developed azotemia had stage C or D disease. Serum LDH prior to chemotherapy correlated well with the stage of disease and predicted the serum levels of creatinine, uric acid and phosphorus in the post-treatment period. Surgical excision of the main tumor mass was associated with a low incidence of azotemia and other metabolic derangements. Hyperuricemia and occasionally obstruction were encountered as the causes of azotemia in the pre-treatment period. Hyperuricemia and/or hyperphosphatemia were presumed responsible for the development of azotemia in the post-chemotherapy period. Two patients were dialyzed for renal failure due to hyperuricemia and one for renal failure due to hyperphosphatemia which developed shortly after starting chemotherapy. The patterns of renal and metabolic disturbances observed during treatment of these patients were characterized by the following profiles: 1. Azotemia due to hyperuricemia prior to treatment. 2. Hyperuricemia without azotemia in the pre-treatment period with azotemia due to hyperphosphatemia in the post-treatment period. 3. Azotemia due to combined hyperphosphatemia and hyperuricemia developing gradually in post-treatment period. 4. Increased urine phosphorus excretion in both non-azotemic and azotemic patients.