Approximately twenty years before this study, a site that consisted of a mixed oak forest was harvested, cleared, and divided into three treatment areas consisting of approximately 20 acres each. The three areas were planted to oak (forest), grass (grassland) and corn (agricultural) respectively. The influence of pH on the rate of phosphatase activity was determined over a broad range of soil pH in soil sampled from each treatment area. Phosphomonoesterase activities were measured at a pH of 2 through 12 and phosphodiesterase activities determined at a pH of 4 through 12. In the forest soil only a acid phosphomonoesterase was detected whose pH optima was maximal at the measured soil pH of 4.9. A neutral phosphomonoesterase was found in the grassland soil, pH 6.6, with a broad pH optima ranging from 4.6 to 7.0, while the detection of an acid phosphatase and a alkaline phosphatase, with a pH optima of 4.8 and 11.0 respectively, was found associated with the agriculture soil with a measured pH of 7.2. Phosphodiesterase activity was optimum or near optimum at the measured pH of each soil examined. The released phosphatases apparently have different pH optima in relation to maximal activity suggesting the presence of different kinds of phosphomonoesterases and phosphodiesterases and perhaps that the enzymatic reaction in soil is catalyzed by more than one enzyme or by multiple forms of the same enzyme. The results of the study would indicate that a relationship exists between soil pH and (1) the synthesis and release of phosphatases in soil, (2) the complexion of the organisms producing the enzymes and (3) phosphatase stability or conformation. Based upon the results of the study, the analysis of phosphatase activity at the measured soil pH would seem to be a necessary part of any investigation designed to determine the contribution of phosphatase enzymes to the cycling of P.