A prospective randomised double blind crossover trial was conducted comparing the new synthetic cannabinoid nabilone with oral domperidone in a group of children receiving repeated identical courses of emetogenic chemotherapy for a variety of malignant diseases. Eighteen of 23 consecutive eligible children, aged 10 months to 17 years, completed the trial. When taking nabilone they experienced significantly fewer vomiting episodes and less nausea, and two thirds expressed a preference for the drug. The most common side effects of treatment with nabilone were somnolence and dizziness, with one patient being disturbed by hallucinations. The results indicate that nabilone is an effective antiemetic for children having chemotherapy, even for young children. It seems to be superior in this respect to domperidone, and although it has a higher incidence of side effects, these are mostly acceptable to patients. It can be recommended as an alternative to conventional antiemetic treatment throughout childhood.