The natural history of a moderate intoxication with botulin (probably type B) in six patients is presented and discussed. All patients complained of a persistent and almost complete failure of accommodation, and marked dryness of the mouth. Reduced lacrimation was also noticeable. A disturbance of efferent pupillary reaction was noted only in four patients, and resolved relatively early. On testing with highly diluted pilocarpine solution, a denervation hypersensitivity reaction of the sphincter pupillae was seen. An optic nerve lesion could not be demonstrated in any of the cases. Manifest involvement of the striated musculature, such as a bilateral lateral rectus palsy and ptosis, was found in only one patient. In four patients the presenting symptom was gastroenteritis. Other systemic symptoms were dysphagia, persistent constipation, problems with micturition, general malaise and postural symptoms. All of the patients made a full recovery at the latest after 10 weeks.