The high cost of hospitalization for hemodialysis patients has become a major health care issue. To address this issue, length of hospital stay and costs for these patients were compared with services covered by nephrologists and services covered by internists. Hemodialysis patients (n = 161) were prospectively admitted 219 times on alternate days to services covered by nephrologists or by internists from July 1995 to March 1996. Admissions to nonmedical services and admissions for overnight observation were excluded. Length of stay, costs, and risk-adjusted predicted length of stay and costs, as well as the number of consultations were compared between services, using Wilcoxon rank sum tests. Readmissions and deaths were compared using chi(2) tests. Mean length of stay for admissions to the nephrology service (n = 114) was 6.3 days compared with 8.1 days for admissions to internal medicine services (n = 105) (P = 0.017). The predicted length of stay was similar. Mean overall cost for admissions under the care of nephrologists was $7,925 versus $10,773 under the care of internists (P = 0.101). The internal medicine service averaged 1.5 consultations versus 0.5 consultations for the nephrology service (P = 0.001). The risk of readmission was 24% for nephrologists and 30% for internists (P = 0.328). Death within 90 days of discharge was 12% for the nephrology group and 22% for the internal medicine group (P = 0.07). The length of stay was significantly shorter for hemodialysis patients under the care of nephrologists compared with internists. The average total costs and risk of readmissions tended to be lower for nephrologists. If these results are corroborated, the care of hemodialysis patients by the nephrologist could diminish the overall expense of the ESRD program.