The existence of a DNase in the supernatant fluid of sonorated Bacillus subtilis strain was confirmed by the viscosimetric determination. The reaction is roughly of the first order and the value of the velocity constant, K, was used to compare the enzyme activity. The optimum pH of this DNase is 8.5. The enzyme is activated by both magnesium and manganese ions. The enzyme is completely destroyed by heating at 70℃ for 5 minutes.