The clinical features of 27 patients identified in an outbreak of botulism in Lancashire, England, and North Wales are reviewed. All but 1 of the patients (age range 14 months to 74 years) were admitted to hospital: 12 were treated in intensive care units, and 8 received positive pressure ventilation. 1 patient died with an aspiration pneumonia. The clinical presentations contained several unusual features, with evidence of segmental demyelination in some patients and drowsiness, sore throats, and fever in others. The widely dispersed source of intoxication with patients presenting singly to several hospitals added to the difficulties of diagnosis. Successful clinical management depends on full and early recognition both of the dangers of impaired oropharyngeal function and of the rapid neurological changes in botulism.