Cannabinoids are used to treat nausea and vomiting. The effect appears to be mediated by cannabinoid receptors in the nucleus tractus solitarius. Results are available from studies on the use of cannabinoids to manage nausea and vomiting after chemotherapy. None of these studies, however, compared cannabinoids with the newer serotonin antagonists. The antiemetic efficacy of cannabinoids for other indications has not yet been studied sufficiently. Most of the studies report significantly more or stronger side effects with cannabinoid medication in comparison to similar medication. In some of the studies on treatment after chemotherapy or radiotherapy, the patients terminated the cannabinoid therapy more frequently due to side effects. Although clinical studies have provided clear evidence for the antiemetic efficacy of cannabinoids, the frequency and severity of side effects argue against their use as the method of first choice. For patients who cannot be adequately treated with conventional antiemetic agents, cannabinoids can represent a valuable adjunct to the antiemetic regimen.