1. The acid and alkaline phosphatase activity has been determined on a series of suspensions of white cells obtained from both man and the rabbit by several different methods.
2. A statistical analysis of the results shows that for both species the alkaline phosphatase of white cell suspensions is confined chiefly to the polymorphonuclear leukocyte and the acid phosphatase is chiefly in the lymphocyte, although the polymonphonuclear leukocyte contains lesser concentrations of this enzyme also.
3. Although this qualitative distribution was the same for both species studied, quantitatively the rabbit differed from man. The activity of the alkaline phosphatase of the rabbit polymorphonuclear leukocyte was eight times that of the corresponding human cell, while the activity of the acid phosphatase of the human lymphocyte was more than twice that of rabbit lymphocyte.