1. The enzyme present in the pneumonic lung exudate still remains active after preservation for 18 months. 2. The enzyme is active at incubator temperature before and after heating to 65 degrees C. for 1 hour. It is slightly active at room temperature and inactive after heating at 75 degrees C. for 1 hour. 3. Dialysis of the enzyme is not demonstrable. 4. Activity persists when the enzyme is mixed with concentrations of sodium chloride varying from normal to thirty-two times normal.