OBJECTIVE: Examine access to recombinant human erythropoietin (rHuEPO) by dialysis-dependent end-stage renal disease (ESRD) patients during the first year after FDA approval for use in clinical practice and Medicare coverage. DESIGN: Longitudinal and cross-sectional claims data analyses. SETTING: All US providers of outpatient dialysis treatment. PATIENTS: 126,201 Medicare-entitled dialysis patients (approximately 93% of all US dialysis patients). OUTCOME MEASURES: Percentage of patients who received rHuEPO, odds of receiving rHuEPO according to patient characteristics, and cost of rHuEPO to Medicare. RESULTS: One year after FDA approval, 52% of all dialysis and 60% of in-center hemodialysis patients who regularly had Medicare-paid dialysis services received rHuEPO at a monthly cost to Medicare of $19 million (18% of Medicare ESRD outpatient expenditures and 6% of all ESRD program expenditures). Blacks were less likely than whites to receive rHuEPO (odds ratio, 0.88; 95% confidence interval, 0.86 to 0.91). Home peritoneal and hemodialysis patients were less likely than in-center hemodialysis patients to receive rHuEPO (odds ratios, 0.17 and 0.22, respectively; 95% confidence intervals, 0.16 to 0.17 and 0.20 to 0.24, respectively). Use of rHuEPO varied across geographic regions. The odds of receiving rHuEPO were lower for patients of male vs female sex, of ages 35 through 64 years vs less than 35 years and greater than 65 years, with a longer history of ESRD, with polycystic kidney disease vs other causes of ESRD, and receiving care in nonprofit vs for-profit facilities. First-month hematocrits were slightly higher (1.2 percentage points) for patients starting rHuEPO in the 12th month than in the first month after FDA approval. CONCLUSIONS: With prompt insurance coverage, the majority of Medicare-entitled dialysis patients received rHuEPO following widespread availability. Factors that may not be related to clinical need (race, setting of care, and geography) possibly influenced early patient access. More attention should be paid to monitoring the appropriate use of high-cost biotechnologic therapy