Since January 1996, we have administered myeloablative therapy followed by infusion of unrelated umbilical cord blood cells in 57 adult patients with high-risk disease. The median age was 31 years (range, 18-58 years), and the median weight was 70 kg (range, 46-110 kg). Two patients were treated for genetic disorders and 55 for advanced hematologic malignancies. The preparative regimens were total body irradiation or busulfan based, both with antithymocyte globulin. HLA matching between donor and recipient was 3 of 6 in 3 patients, 4 of 6 in 44 patients, 5 of 6 in 8 patients, and 6 of 6 in 2 patients. The median nucleated cell dose was 1.50 x 10(7)/kg (range, 0.54-2.78 x 10(7)/kg), and the median CD34(+) cell dose was 1.37 x 10(5)/kg (range, 0.02-12.45 x 10(5)/kg). All patients received granulocyte colony-stimulating factor after transplantation until neutrophil recovery. Graft-versus-host disease prophylaxis consisted of cyclosporine and steroids. The median number of days to an absolute neutrophil count of 500/microL was 26 (range, 12-55 days). The median time to an untransfused platelet count of >20000/microL was 84 days (range, 35-167 days). Seventeen patients developed grade II to IV acute GVHD. The median survival of the entire group was 91 days (range, 10-2251 days). Eleven patients were alive at a median follow-up of 1670 days (range, 67-2251 days), 1 with autologous recovery and 1 with relapsed lymphoma. The actuarial projected 3-year survival is 19%. Infection was the primary cause of death. These results suggest that unrelated umbilical cord blood transplantation is a viable option for adult patients and should be explored in patients with earlier-stage disease.