This phase II trial evaluated the safety and efficacy of combining yttrium-90 (90Y) ibritumomab tiuxetan with high-dose carmustine, cytarabine, etoposide, and melphalan (BEAM) and autologous stem-cell transplantation in patients with non-Hodgkin's lymphoma who were considered ineligible for total-body irradiation because of older age or prior radiotherapy. Between May 2002 and January 2006, 14 days before autologous stem-cell transplantation, 41 patients with non-Hodgkin's lymphoma received standard-dose 90Y ibritumomab tiuxetan (14.8 MBq/kg [0.4 mCi/kg]) followed by high-dose BEAM. The median age was 60 years (range, 19 to 78 years), and the median number of previous therapies was two (range, one to six). Disease histologies were diffuse large B-cell (n = 20), mantle cell (n = 13), follicular (n = 4), and transformed lymphoma (n = 4). With a median follow-up of 18.4 months (range, 5.5 to 53.3 months) the estimated 2-year overall and progression-free survival were 88.9% (95% CI, 75.3% to 95.2%) and 69.8% (95% CI, 56.4% to 79.7%). The median time to WBC engraftment was 11 days (range, 9 to 26 days) and time to platelet engraftment was 12 days (range, 3 to 107 days). Adverse events were similar to those seen historically with high-dose BEAM alone, and included grade 3 or 4 pulmonary toxicity in 10 patients. Adding 90Y ibritumomab tiuxetan to high-dose BEAM with autologous stem-cell transplantation is feasible and has a toxicity and tolerability profile similar to that observed with BEAM alone. Rates of progression-free survival seen in these patients are promising and warrant additional study.