Eighty patients receiving their first course of chemotherapy with regimens containing cisplatin or cisplatin analogues entered this open crossover study comparing nabilone 2 mg and prochlorperazine 5 mg given orally every 12 h for four doses against metoclopramide 2 mg/kg loading dose intravenously (i.v.), then 3 mg/kg as an (i.v.) infusion over 8 h and dexamethasone 20 mg (i.v.) over 3-5 min at the time of chemotherapy. There was complete control of nausea and vomiting in 24 patients (32%) given metoclopramide and dexamethasone compared to 14 patients (19%) given nabilone and prochlorperazine. For the 70 patients who completed the crossover assessment of emesis on a linear analogue scale significantly favoured metoclopramide and dexamethasone (P = 0.02). However, there was no overall patient preference for the metoclopramide and dexamethasone combination (nabilone and prochlorperazine 31 vs. metoclopramide and dexamethasone 26; 13 no preference), because a significant proportion of the patients receiving the cisplatin analogue carboplatin preferred nabilone and prochlorperazine (16 vs. 5; 1 no preference; P = 0.013). For patients receiving cisplatin chemotherapy metoclopramide and dexamethasone remains the antiemetic of choice but for regimens containing carboplatin, nabilone and prochlorperazine is better tolerated and preferred by the patients.