In some parts of the world, medicinal cannabinoids have already been used to treat nausea and vomiting associated with chemotherapy and wasting in diseases such as AIDS and terminal cancer. However, over the last several years, currently used cannabinoids, such as dronabinol, as well as newly developed cannabis-based medicines such as Sativex® (narrow ratio combination of Δ9-tetrahydrocannabinol and cannabidiol), have been investigated for the treatment of spasticity, chronic pain, disruption of sleep and urinary dysfunction associated with multiple sclerosis and other neurological disorders. Although some clinical trials have yielded positive results, others have not and there has been controversy regarding the use of subjective rating scales to measure pain and spasticity. Adverse side effects have been generally mild and transient; however, researchers and clinicians are still concerned about the prospect of long-term adverse side effects. This review will summarise and critically evaluate the currently available clinical trial data.