This prospective trial evaluated the efficacy and toxicity of granisetron for antiemetic control in patients receiving high-dose cyclophosphamide (CY)-containing regimens with/without TBI for bone marrow (BM) or peripheral blood stem cell (PBSC) transplantation or PBSC mobilization. Granisetron 1 mg i.v. plus dexamethasone 10 mg i. v. were administered daily 30 min before chemotherapy or radiation for a median of 5 days. Response was defined as the number of emetic episodes per 24 h: complete response, 0 and no emetic rescue; major response, 1-2; minor response, 3-5; failure, >5. One hundred patients were enrolled. Ninety-eight received CY-containing regimens and 26 of these additionally received TBI (12 Gy divided over 4 days). Response was complete on 216 (47%) of a total 456 patient days, major on 222 (49%), minor on 14 (3%), and failure on 4 (1%). Mean number of emetic episodes per patient per day and breakthrough medication required per patient per day was 0.24 (range 0-8) and 0. 40 (range 0-8), respectively. Adverse effects were minimal, with headache (20%) reported most frequently. Based on these results, granisetron plus dexamethasone is an effective and well-tolerated antiemetic regimen in BMT/PBSCT recipients conditioned with high-dose chemotherapy with/without TBI. Bone Marrow Transplantation (2000) 25, 1279-1283.