Patients receiving outpatient chemotherapy, without cisplatin, were randomised to receive four doses of either domperidone 60 mg or prochlorperazine 25 mg suppositories every 4 h, starting 30 min before the chemotherapy. They were crossed over for the next chemotherapy cycle. To enable analysis of 100 patients who had received identical chemotherapy in each course, 136 patients were randomised. Patients experienced a higher grade of nausea on domperidone (P = 0.05). Only 18% of patients vomited on domperidone and 14% on prochlorperazine, but the number of vomits was higher on domperidone (P = 0.003) and the duration was significantly increased (P = 0.02). Patients experienced significantly more diarrhoea on domperidone (P < 0.0001), although it was predominantly mild. Patients were significantly more sedated on prochlorperazine on the second course (P = 0.006), but not on the first course (P = 0.9). More patients preferred their second course (P < 0.0001), and were significantly less anxious (P = 0.0002). Patients reported tolerating their treatment similarly for both antiemetics, but more patients preferred prochlorperazine (P = 0.003), mainly due to reductions in nausea and vomiting and other side-effects, particularly diarrhoea.