The authors conducted a randomized, double-blind, placebo-controlled, twofold crossover study in 16 patients with MS who presented with severe spasticity to investigate safety, tolerability, and efficacy of oral Delta(9)-Tetrahydrocannabinol (THC) and Cannabis sativa plant extract. Both drugs were safe, but adverse events were more common with plant-extract treatment. Compared with placebo, neither THC nor plant-extract treatment reduced spasticity. Both THC and plant-extract treatment worsened the participant’s global impression.