Abstract. Mortality rates in ESRD are unacceptably high. Disorders of mineral metabolism (hyperphosphatemia, hypercalcemia, and secondary hyperparathyroidism) are potentially modifiable. For determining associations among disorders of mineral metabolism, mortality, and morbidity in hemodialysis patients, data on 40,538 hemodialysis patients with at least one determination of serum phosphorus and calcium during the last 3 mo of 1997 were analyzed. Unadjusted, case mix-adjusted, and multivariable-adjusted relative risks of death were calculated for categories of serum phosphorus, calcium, calcium ϫ phosphorus product, and intact parathyroid hormone (PTH) using proportional hazards regression. Also determined was whether disorders of mineral metabolism were associated with all-cause, cardiovascular, infection-related, fracture-related, and vascular access-related hospitalization. After adjustment for case mix and laboratory variables, serum phosphorus concentrations Ͼ5.0 mg/dl were associated with an increased relative risk of death (1.07, 1.25, 1.43, 1.67, and 2.02 for serum phosphorus 5.0 to 6.0, 6.0 to 7.0, 7.0 to 8.0, 8.0 to 9.0, and Ն9.0 mg/dl). Higher adjusted serum calcium concentrations were also associated with an increased risk of death, even when examined within narrow ranges of serum phosphorus. Moderate to severe hyperparathyroidism (PTH concentrations Ն600 pg/ml) was associated with an increase in the relative risk of death, whereas more modest increases in PTH were not. When examined collectively, the population attributable risk percentage for disorders of mineral metabolism was 17.5%, owing largely to the high prevalence of hyperphosphatemia. Hyperphosphatemia and hyperparathyroidism were significantly associated with all-cause, cardiovascular, and fracturerelated hospitalization. Disorders of mineral metabolism are independently associated with mortality and morbidity associated with cardiovascular disease and fracture in hemodialysis patients.At present, Ͼ300,000 people in the United States are undergoing therapy for ESRD with the majority on in-center hemodialysis (1). Although extending the life of patients with ESRD should be considered one of the great medical accomplishments of the latter half of the 20th century, much remains to be improved. Mortality rates are in excess of 20% per year despite improved dialytic technology and the expenditure of considerable resources, Ͼ$22 billion per year as of 2001 (1).Numerous studies have attempted to identify risk factors for mortality and morbidity in this population. Most have shown important relations among demographic factors (e.g., older age, male gender, white race) and mortality (2,3). Comorbid conditions (e.g., diabetes, cardiovascular disease) and laboratory proxies of nutritional status (e.g., serum albumin, prealbumin, creatinine) have also been consistently associated with mortality and morbidity (4 -6). Unfortunately, few of these factors are mutable. Of those factors that potentially are influenced by changes in dialysis practice, the in...