In order to describe renal involvement in aggressive non-Hodgkin's lymphomas (NHLs) and its prognostic significance, we reviewed the outcome of 48 patients with renal involvement treated with the LNH-84 or LNH-87 regimen. Histology was diffuse large cell in 29 (60%) patients; immunoblastic, diffuse mixed cell and lymphoblastic in four each; follicular large cell, diffuse small cleaved cell and diffuse small non-cleaved cell in one each; and unclassified in four. Ann Arbor stage was IV in 44 patients, and IE or IIE in four. Tumour mass > or = 10 cm, performance status (ECOG scale) > 2 and increased LDH level were present in 69%, 20% and 76% of patients respectively. Fifteen patients (31%) had multiple intraparenchymal nodules, 14 (29%) had direct spread into the kidney from a perirenal mass, ten (21%) had a single intraparenchymal nodule and nine (19%) had diffuse infiltration. Twenty-one patients (43%) presented with bilateral lesions. Three patients (6%) presented with acute renal failure. Ten other patients (21%) had serum creatinine > 120 mumol l-1. In 12 of these 13 patients renal function was restored with chemotherapy. Twenty-eight patients (57%) achieved complete remission. Estimated 4 year disease-free survival was 39%. Disease-free survival and actuarial survival at 4 years were estimated to be 58% respectively. Two renal parameters had adverse prognostic significance for survival: renal hilum involvement (P = 0.02) and diffuse renal infiltration (P = 0.01). A Cox model identified only two independent prognostic factors for survival, namely performance status > or = 2 and tumour size > or = 10 cm. We conclude that alteration in renal function occurs in 27% of patients with renal involvement. Systemic chemotherapy improves renal function rapidly. Long-term outcome is similar to that expected in NHL patients presenting with the same prognostic factors.