Botulism was suspected in a 17-day-old breastfed infant who developed over 2 days progressive muscular weakness and hypoventilation. The patient also presented with pupil dilation and light unresponsiveness. The electroencephalogram was normal. Full recovery was obtained after 85 days of artificial ventilation. Diagnosis was confirmed by the presence of the botulin toxin B in the patient serum. The source of the infection was not identified.