Objective: To evaluate renal involvement in childhood lymphoma and define its prognostic effects. Patients and Methods: One hundred and four patients with non-Hodgkin's lymphoma and renal involvement on admission to a single center between 1972 and 2003 were evaluated retrospectively. Blood urea nitrogen, serum creatinine, uric acid, electrolytes, and lactate dehydrogenase levels, as well as urinalysis, were evaluated. One or more of the following imaging methods were performed: intravenous urogram, ultrasound, computed tomography, and magnetic resonance imaging. The chi(2) test was used to compare the groups. The Kaplan-Meier survival method was used to calculate survival rates, and the log-rank test was used to compare groups with respect to survival. Survival rates were also compared in two different time periods (before 1991 and after 1991). Results: There were 76 boys and 28 girls with a median age of 6 (0.9-16) years. The renal infiltration pattern was nodular in 62 patients (59.6%) and diffuse in 40 patients (38.5%). Two patients had tumoral masses that originated from their kidneys (1.9%). Renal involvement was bilateral in 75 patients (72.1%); the remaining 29 patients had unilateral involvement. The overall survival rate was 42.5% with a median follow-up of 64 months. The factors that had a statistically significant impact on survival were high creatinine (p = 0.00001) and blood urea nitrogen levels (p = 0.0001), the onset of tumor lysis syndrome (p = 0.01), and the need for dialysis (p = 0.009). The survival rate was higher in the time period after 1991 (p = 0.01). Conclusion: Impaired renal function is a poor prognostic factor for non-Hodgkin's lymphoma. Renal function should therefore be monitored closely. Renal dysfunction caused by direct tumoral involvement may complicate therapy and shorten survival. Copyright (C) 2005 S. Karger AG, Basel.