Keywords: antiemetic; bone marrow transplant; chemotherapy; dexamethasone; granisetron; total body irradiation Nausea, retching, and emesis are some of the most common unwanted effects associated with chemotherapy. These treatment side-effects represent a significant concern to the cancer patient.1 Nausea and vomiting are contributing factors to patient morbidity, and are critical factors in the patient's quality of life during treatment. Additionally, emetic episodes often influence the continuation of treatment.2 Fortunately, with the advent of the serotonin antagonists, there has been a major improvement in the control of nausea and vomiting.3 Granisetron is a potent, selective 5-hydroxytrypamine 3 (5-HT 3 ) receptor antagonist that has activity both in the periphery on the abdominal vagal afferents, and centrally on the chemoreceptor trigger zone (CTZ). Emesis occurs when the vomiting center is stimulated by the CTZ or by afferent impulses from the cerebral cortex, gastrointestinal tract, heart, or vestibular apparatus. 4Several receptor types have been identified in these regions, including dopaminergic, cholinergic, histaminergic, opioid, and serotonergic (5-HT 3 ). 5 Chemotherapy and radiotherapy cause cellular damage, eliciting a release of serotonin from enterochromaffin cells in the intestinal mucosa. Serotonin release also activates 5-HT 3 receptors in the vagal and possibly splanchnic afferent neurons through agonism with resultant stimulation of the CTZ, causing the vomiting reflex.6 Granisetron controls chemotherapy-induced nausea and vomiting via competitive antagonism of serotonin at the 5-HT 3 receptors. 7Granisetron is FDA-approved for the prevention of nausea and vomiting associated with initial and repeated courses of emetogenic cancer chemotherapy. Several trials have addressed the antiemetic efficacy of serotonin antagonists for the prevention of irradiation-induced emesis. [7][8][9][10][11] The controversies that currently exist regarding granisetron use in this patient population include optimal dose and optimal dosing frequency. 11,12The main objectives of this trial were to monitor the emetic control of granisetron plus dexamethasone in patients who received chemotherapy regimens containing high-dose CY with or without TBI as a preparative regimen for BM or PBSC transplantation or PBSC mobilization, and evaluate any adverse effects of the combination. Patients and methods Study designThis study was a single-center, open-label, prospective trial approved by the Institutional Review Board. Written informed consent was obtained from all patients prior to enrollment. All patients had either a hematologic or oncologic malignancy. Patients were eligible if they were receiving any high-dose chemotherapy preparative regimen containing cyclophosphamide (CY) (у60 mg/kg/day or у1.5 g/m 2 /day) with or without TBI (12 Gy divided over 4 days), followed by BM or PBSC transplantation or PBSC mobilizaton. Additionally, patients had to be 16 years or