A multi-centre, double-blind study was carried out in 100 patients suffering from chronic spasticity due to multiple sclerosis to compare the effectiveness of tizanidine hydrochloride with that of baclofen. Patients were allocated at random to receive treatment initially with daily doses of either 6 mg tizanidine or 15 mg baclofen and the dose was increased during the first 2 weeks up to a maximum of 24 mg tizanidine or 60 mg baclofen per day. Patients were then treated with the optimum dose for 6 weeks. Efficacy and tolerability parameters were evaluated after 2 and 8 weeks. Tizanidine and baclofen improved the functional status of patients in 80% and 76% of cases, respectively, but there were no significant differences between the two drugs. The antispastic efficacy of tizanidine was greater after 8 weeks than after 2 weeks, whereas the efficacy of baclofen decreased slightly with time. Both drugs showed good overall tolerability in more than 60% of patients. Thus, tizanidine is a well tolerated and effective muscle relaxant, the antispastic efficacy of which is well maintained over time, and it promises to be particularly useful in the treatment of spasticity due to multiple sclerosis.