Levonantradol is a cannabis derivative. Cannabinoid anti-emetics are being assessed in cancer chemotherapy but have been little used in radiotherapy to date. A pilot study and randomised trial compared the anti-emetic effect of a standard drug (Chlorpromazine 26 mg) with Levonantradol at two doses (0.5 and 0.75 mg) in patients receiving palliative single fraction radiotherapy to sites likely to cause nausea and vomiting. Most patients were out-patients. Both drugs were well tolerated. The frequency of vomiting was similar in all three groups in both the pilot study and randomised trial.