Purpose: To assess the antiemetic effects and safety profile of four different doses of granisetron (Kytril; SmithKline Beecham Pharmaceuticals, Philadelphia, PA) when administered as a single intravenous (IV) dose for prophylaxis of cisplatin-induced nausea and vomiting. Patients and Methods: One hundred eighty-four chemotherapy-naive patients receiving high-dose cisplatin (81 to 120 mg/m2) were randomized to receive one of four granisetron doses (5, 10, 20, or 40 μg/kg) administered before chemotherapy. Patients were observed on an inpatient basis for 18 to 24 hours, and vital signs, nausea, vomiting, retching, and appetite were assessed. Safety analyses included incidence of adverse experiences and laboratory parameter changes. Results: After granisetron doses of 5, 10, 20, and 40 μg/kg, a major response (≤ two vomiting or retching episodes, and no antiemetic rescue) was recorded in 23%, 57%, 58%, and 60% of patients, respectively, and a complete response (no vomiting or retching, and no antiemetic rescue) in 18%, 41%, 40%, and 47% of patients, respectively. There was a statistically longer time to first episode of nausea (P = .0015) and vomiting (P = .0001), and fewer patients were administered additional antiemetic medication in the 10-μg/kg dosing groups than in the 5-μg/kg dosing group. As granisetron dose increased, appetite return increased (P = .040). Headache was the most frequently reported adverse event (20%). Conclusion: A single 10-, 20-, or 40-μg/kg dose of granisetron was effective in controlling vomiting in 57% to 60% of patients who received cisplatin at doses greater than 81 mg/m2 and totally prevented vomiting in 40% to 47% of patients. There were no statistically significant differences in efficacy between the 10-μg/kg dose and the 20- and 40-μg/kg doses. Granisetron was well tolerated at all doses.