Spasticity represents a common troublesome symptom in patients with multiple sclerosis (MS). Treatment of spasticity remains difficult, which has prompted some patients to self-medicate with and perceive benefits from cannabis. Advances in the understanding of cannabinoid biology support these anecdotal observations. Various clinical reports as well as randomized, double-blind, placebo-controlled studies have now demonstrated clinical efficacy of cannabinoids for the treatment of spasticity in MS patients. Sativex is a 1:1 mix of delta-9-tetrahydocannabinol and cannabidiol extracted from cloned Cannabis sativa chemovars, which recently received a label for treating MS-related spasticity in Germany. The present article reviews the current understanding of cannabinoid biology and the value of cannabinoids as a symptomatic treatment option in MS.