Intact spores of Bacillus subtilis are susceptible to subtilopeptidase attack and this enzymatic reaction induces changes in the spore similar to those that take place during "physiological" germination. Germination occurred between pH 5.5 and 10.0 showing a pH optimum of 9.0 and between 25 °C and 45 °C with an optimum of 37–40°. Subtilopeptidase-induced germination took place in completely anaerobic conditions. Sublethal heating of spore suspensions increased the rate of subtilopeptidase-induced germination. Germination with subtilopeptidase was almost completely inhibited by an excess of diisopropyl fluorophosphate. L-Alanine-induced germination was not affected by diisopropyl fluorophosphate. Participation of the spore metabolism in subtilopeptidase-induced germination seemed likely. These results suggest that subtilopeptidases initiate spore germination by releasing germination agents from the spore.No significant loss of viability was noted until after exposure to the proteolytic enzyme for at least 60 minutes. Prolonged exposure of B. subtilis spores to subtilopeptidase results in death of the exposed spores.Subtilopeptidase-induced germination was also observed in several spores of other members of the genus Bacillus.