"Shaker foal" disease, toxicoinfectious botulism of foals, was 1st described as a clinical entity in 1967. The reported mortality rate was 90%, with death occurring within 24-72 hours of the onset of the characteristic clinical signs. The mortality rate decreased when equine-origin botulism antitoxin became available; however, a certain percentage of foals continued to die of respiratory failure. Mechanical ventilation is an important part of the treatment of infant botulism and is essential to the survival of many affected infants. We report a retrospective study of 9 foals with toxicoinfectious botulism where early mechanical ventilation was employed as part of the treatment. Foals receiving mechanical ventilation were progressively acidemic and had increased PaCO2 tensions before mechanical ventilation. These arterial blood gas abnormalities were ameliorated with mechanical ventilation. One foal was euthanized for economic reasons; survival in treated foals was 87.5%. Mechanical ventilation of foals with botulism and respiratory failure appears to be an effective therapy.