Sixteen patients suffering from spasticity due to multiple sclerosis were treated with baclofen and tizanidine in a partially blind cross-over study. No significant difference in efficacy was found. The most striking difference was seen in the side-effects: baclofen frequently caused more or less severe muscle weakness and even falling during walking and standing. Treatment with tizanidine produced an apparent improvement of mobility in some patients suffering from moderate or marked paresis associated with a marked spasticity of their legs. Isometric muscle strength did not show any significant changes during either treatment. The different impact of baclofen and tizanidine on mobility and weight support seems to be related to their different site of action in spasticity.