The original clinical application of botulinum neurotoxin was in the treatment of strabismus by local chemical denervation of the neuromuscular junction and relaxation of the muscle with a duration of several months. This initial application has been followed by use of the neurotoxin to treat a wide range of disorders of muscle hyper-contraction. Botulinum neurotoxin is now a major clinical product for the treatment of spasticity and muscle hyperactivity. Muscle relaxation also underpins the cosmetic use of the neurotoxin. This chapter will review and assess the clinical utility of the various botulinum products in neuromuscular disorders.