BACKGROUND: Elevated serum phosphorus and calcium are associated with arterial calcification and mortality in dialysis patients. Sevelamer, a phosphate-binding polymer, attenuates the progression of arterial calcification; it is unknown whether this improves outcomes. PATIENTS AND INTERVENTIONS: A randomized comparison of sevelamer and calcium-based phosphate binders was performed in hemodialysis patients treated up to 45 months. The primary endpoint was mortality. Secondary endpoints included cause-specific mortality and hospitalization; 2103 patients were randomized, 2040 received treatment, and 1065 completed treatment. RESULTS: Overall mortality was not significantly reduced by sevelamer (adjusted relative risk = 0.92; 95% confidence interval, 0.78 to 1.09; log-rank P = .40). Among patients > or = 65 years of age, sevelamer reduced the risk of death (adjusted relative risk = 0.77; 95% confidence interval, 0.62 to 0.97; log-rank P = .02). Sevelamer patients had a trend toward fewer hospitalizations (P = .06) and fewer hospital days (P = .09). CONCLUSIONS: A statistically significant reduction in mortality in the overall study population was not observed. Sevelamer was associated with a survival benefit among patients > or = 65 years of age.