Animal studies suggest that calcium-phosphorus homeostatic abnormalities cause cardiovascular disease in uremia; few observational studies in humans have explored this. Associations in the retrospective United States Renal Data System Waves 1, 3, and 4 Study of 14,829 patients who were on hemodialysis on December 31, 1993, were examined. Mean age and duration of renal replacement therapy were 60.0 and 3.2 yr, respectively; 40.7% had diabetes. Quintiles (Q 1 to Q 5 ) of (albumin-adjusted) calcium were <8.7, 8.8 to 9.2, 9.3 to 9.6, 9.7 to 10.2, and >10.2 mg/dl; phosphorus, <4.4, 4.5 to 5.3, 5.4 to 6.3, 6.4 to 7.5, and >7.5 mg/dl; calcium-phosphorus product, <40.9, 41.0 to 50.1, 50.2 to 59.2, 59.3 to 71.0, and >71.0 mg 2 /dl 2 ; and parathyroid hormone (PTH), <37, 38 to 99, 100 to 210, 211 to 480, and >480 pg/ml. Higher calcium levels were associated with fatal or nonfatal cardiovascular events (adjusted hazards ratio, 1.08 for Q 5 , versus Q 1 ) and all-cause mortality (Q 2 , 1.07; Q 4 , 1.11; Q 5 , 1.14). Phosphorus levels were associated with cardiovascular events (Q 2 , 1.06; Q 3 , 1.13; Q 4 , 1.14; Q 5 , 1.25) and mortality (Q 4 , 1.10; Q 5 , 1.19), calcium-phosphorus product was associated with cardiovascular events (Q 3 , 1.09; Q 4 , 1.14; Q 5 , 1.24) and mortality (Q 4 , 1.09; Q 5 , 1.19), and PTH levels were associated with cardiovascular events (Q 5 , 1.12) and mortality (Q 5 , 1.17). Despite limitations (including retrospective design; noncurrent study era; and lack of serial calcium, phosphorus, and PTH measurements), this study suggests that disorders of calcium homeostasis are associated with fatal and nonfatal cardiovascular events and all-cause mortality in hemodialysis patients.