One hundred thirty-two doses of botulinum A toxin were injected into 42 humans. The effect on horizontal strabismus was uniformly beneficial, and effect lasting up to 411 days since the last injection was documented. The effect in vertical strabismus and lid retraction was beneficial, but less strongly so. No systemic effect or local complications were encountered except for effect on adjacent muscles. The drug appears to be a safe and useful therapy for strabismus.