We examined the prevalence of vitamin D deficiency in hemodialysis patients and tested the hypothesis that decreased levels of 25-hydroxyvitamin D (25D) are associated with an increased risk for early all-cause mortality. One hundred and two patients, 57 (56%) men and 45 (44%) women, mean age 60.5 +/- 13.1 years, were included in our study. Serum calcium and phosphorus levels were measured by routine laboratory methods. Parathyroid hormone (PTH) was measured by immunoassay and 25D by enzyme immunoassay. Patients were divided into two groups depending on the serum concentration of 25D: below or above 50 nmol/L. Survival rates were analyzed using the Kaplan-Meier survival curves. The Cox regression model was used to define potential variables effecting all-cause mortality. The mean level of 25D in all patients was 58 +/- 35.6 nmol/L, 52% of patients had 25D levels >50 nmol/L and 48% had levels of 10.5-50 nmol/L. Compared with men, women were more likely to be 25D deficient (67% vs. 37%; P = 0.005). Patients were observed from the date of laboratory measurement until their death or to a maximum of 730 days. Kaplan-Meier survival analysis showed that mortality in patients was significantly higher in the group with 25D levels < or =50 nmol/L (P < 0.033). With Cox multivariable regression modeling, the PTH level (P < 0.029) turned out to be the only predictor of mortality in our patients. Using the definitions recommended in the National Kidney Foundation Kidney Disease Outcomes Quality Initiative guidelines, we found that our hemodialysis patients on average have vitamin D insufficiency. Our results indicate that patients with 25D levels < or =50 nmol/L are associated with higher all-cause early mortality.