We studied six patients with type A botulism to determine the degree of initial respiratory compromise and to quantitate the time course and extent of recovery of the ventilatory and upper airway muscles and exercise performance. The VM weakness was identified in all patients early after botulism. Upper airway muscle weakness was also common, requiring intubation for airway protection in one patient. Recovery of VM and upper airway muscle strength occurred in all patients, predominantly over the first 12 weeks but continued up to one year in several. A similar time course of improvement was noted for exercise performance. Ventilatory limitation was an unusual cause for exercise limitation. By 12 months, lung function, VM and upper airway muscle strength and exercise performance had returned to normal in all but one patient. We conclude that VM and upper airway muscle weakness occurs in most patients with clinically significant type A botulism.