Medical records of 55 patients with type A and type B food-borne botulism reported to the Centers for Disease Control during 2 years were reviewed to assess the clinical features and severity of illness, diagnostic test results, nature of complications, amd causes of death. Some patients had features not usually associated with botulism including paresthesia (14%), asymmetric extremely weakness (17%), asymmetric ptosis (8%), slightly elevated cerebrospinal fluid protein values (14%), and positive responses to edrophonium chloride(26%). Several observation suggest that type A was more severe than type B disease. Although the case-fatality ratio was not significantly greater, patients with type A disease saw a physician earlier in the course of illness, were more likely to need ventilatory support, and were hospitalized longer. Patients who died were older than those who survived. Deaths within the first 2 weeks resulted from failure to recognized the severity of the disease or from pulmonary or systemic infection whereas the three late deaths were related to respirator malfunction.