Guanidine hydrochloride was introduced as an adjunct in the treatment of botulism in 1968. It has been reported to be of benefit in 39 cases and of no benefit in 13 cases. No serious side effects have occurred with the short-term therapy required in botulism. Our two cases are similar to earlier cases in that the improvement seen with quanidine therapy is most notable in ocular muscles and least notable in respiratory muscles. Electrophysiological findings again showed an increase in the amplitude of evoked muscle-action potentials after guanidine administration.