When solutions containing glucose and phosphate were autoclaved, substances formed which altered the growth response ofClostridium botulinum 62A. Some of these substances were stimulatory and decreased the time required for the appearance of turbidity in liquid cultures. Other substances were inhibitory and delayed the appearance of growth. The inhibitory substances were removed from solution by adsorption on activated charcoal. The concentration of inhibitory substances increased with time of storage of media and autoclaved phosphate-glucose supplement.