Chronic kidney dysfunction is associated with increased mortality in multiple cancer types. Preliminary evidence suggests the same to be true for B-large cell lymphomas (B-LCL). To analyze the relationship of glomerular filtration rate (GFR) and outcome of B-LCL in detail we collected data on outcomes of 285 consecutive patients with newly diagnosed B-LCL treated at our institution with standard rituximab-containing regimens who did not have preexisting kidney disease or urinary tract obstruction at presentation. Median age was 59, range 18 to 87, 145 were male and 140 females. Forty-four had GFR < 60 mL/min, 123 had 60 to 90 mL/min, and 118 > 90 mL/min. Median follow-up of surviving patients was 49 months and estimated 3-year survival 76%. In univariate analysis age (P < .001), GFR (P = .014), stage (P < .001), performance status (P = .044), chemotherapy regimen (P < .01), and international prognostic index (IPI) (P < .001) were statistically significant prognostic factors. In multivariate analysis, age and GFR remained the only independent prognostic factors. Subtracting 1 from the IPI score of patients who had GFR > 90 mL/min and IPI > 1 resulted in a prognostic index that divides patients into 3 prognostic groups (low risk = 0-1, intermediate risk = 2-3 and high risk = 4-5) with an acceptable patient distribution frequency (38%, 39%, and 23%, respectively) and improved statistical significance and separation in comparison to IPI (5-year survival rates of 92%, 74%, and 42%, respectively). GFR is an important independent prognostic factor for B-LCL that should be taken into account in clinical decision making and data analysis and probably be incorporated in prognostic indices.