12 cases of food-borne botulism were registered in Sion, Switzerland, between 31 December, 1993 and 12 January, 1994. A type B toxin was isolated from the serum of one patient and from the incriminated ham. Clinical data of 10 male patients aged 21 to 54 years and some epidemiologic data are reported. The clinical course was mild to moderate with predominant autonomic and gastro-intestinal symptoms and signs: blurred vision (10 patients of 10), dry mouth with dysphagia (9/10), asthenia (7/10), diarrhea and/or constipation (7/10), nausea and vomiting (6/10), abdominal cramps (5/10), impaired sexual function (5/10), dilated pupils (4/10). Some discomfort (mainly blurred vision, asthenia and impaired sexual function) persisted for several months in most patients. Neuromuscular involvement was never the reason for seeking medical assistance and had often disappeared at the time of the first visit. Two patients were hospitalized, one for transient ileus of unknown origin and the second (first suspected case) for monitoring and infusion of trivalent equine botulinum antitoxin. This treatment was administered on day eight after intoxication and had no effect on this patient's outcome when compared with others. No patient died. Epidemiology, diagnosis, treatment and prognosis of botulism are discussed.