Renal involvement is a common finding in non-Hodgkin's lymphoma (NHL). Acute renal failure at initial presentation due to lymphomatous infiltration of the kidneys has been described infrequently. We report a 17-year-old male who presented with acute renal failure due to massive lymphomatous infiltration of the kidneys, which necessitated hemodialysis. The diagnosis of B-cell NHL was established by tru-cut biopsy of the kidneys and the patient had an excellent response to high-dose chemotherapy with no major complication. The presence of extrarenal involvement in the testes and the retroperitoneal lymph nodes made the diagnosis of primary renal lymphoma debatable. However, considering the delay in diagnosis and the high proliferative rate of B-cell NHL, we might postulate that the disease had originated primarily in the kidneys. We recommend that in NHL cases with severe renal involvement, full-dose chemotherapy should be instituted with meticulous clinical and laboratory follow-up in order to improve clinical and renal failure status rapidly and to avoid further dissemination of NHL.