For many years, multiple sclerosis (MS) patients have been self-medicating with illegal street cannabis to alleviate symptoms associated with MS. Data from animal models of MS and clinical studies have supported the anecdotal data that cannabis can improve symptoms such as limb spasticity, which are commonly associated with progressive MS, by the modulation of excessive neuronal signalling. This has lead to cannabis-based medicines being approved for the treatment of pain and spasticity in MS for the first time. Experimental studies into the biology of the endocannabinoid system have revealed that cannabinoids have activity, not only in symptom relief but also potentially in neuroprotective strategies which may slow disease progression and thus delay the onset of symptoms such as spasticity. This review appraises the current knowledge of cannabinoid biology particularly as it pertains to MS and outlines potential future therapeutic strategies for the treatment of disease progression in MS.