Nearly all patients with multiple sclerosis (MS) will develop spasticity in the course of their disease. This symptom accounts for most of the handicap and impairment in the quality of life. Treatment with botulinum toxin will enable an efficient and safe alleviation of spasticity and the problems involved, given a realistic definition of the therapeutic target and a graded multimodal approach. Treatment may fail for a great number of reasons that require diligent analysis. Compared with other disorders resulting in spasticity as well, MS does not constitute a monophasic disorder but is influenced by many factors. Treatment of spasticity in MS must therefore be guided by its particular aspects.