To conduct a meta-analysis of the antispastic efficacy and tolerability of tizanidine, we reviewed records of the European sponsor of tizanidine trials and selected double-blind, randomized studies of moderate duration in which oral tizanidine was compared with baclofen or diazepam. Studies were required to have individual patient data; three key outcome measures (Ashworth Rating Scale for muscle tone, a measure of muscle strength, and Global Tolerability to Treatment Rating); and patients with multiple sclerosis or cerebrovascular lesions. Ten trials involving 270 patients met these criteria. Seven studies used baclofen as the positive control; three used diazepam. As measured by Total and Lower Body Ashworth scores, tizanidine and similar spasticity-reducing effects to both baclofen and diazepam. Muscle strength was affected less by tizanidine than by either comparator, and investigators judged tizanidine to have greater tolerability. Within the limits of these comparisons, tizanidine, baclofen, and diazepam were equally effective in decreasing excessive muscle tone in patients with multiple sclerosis or cerebrovascular lesions. Muscle strength improved in all three treatment groups, but improvement was greatest with tizanidine.