Experiments were conducted to determine the effects of dietary phytase on phosphorus (P) utilization by striped bass, Morone saxatilis, fed high phytate diets. Experiments one and two were designed to determine the effectiveness of various levels of dried and liquid phytase treatments incorporated into striped bass diets. The experiments used different basal diets containing over 70% plant sources and containing 0.45-0.55 % total P and 0.12-0.19% available P. A diet containing potassium monophosphate (PMP) and 0.9% total P (0.5% available P) with no added phytase was used as the positive control. The diets were assigned to duplicate tanks and fed to juvenile striped bass for up to 14 weeks. The effectiveness of the phytase treatments was determined by measuring weight gain, feed conversion, serum, scale and vertebral P, and apparent P digestibility. In experiment one, significant differences (p<0.05) were found in scale and vertebral phosphorus concentrations with 2400 PU/kg diet. In experiment two, significant differences were observed in serum phosphorus between the phytase and no phytase groups while there were no differences between the positive control and the phytase treated fish. It was concluded that 2400 PU/Kg of liquid enzyme resulted in equal bone mineralization and serum phosphorus concentrations as that observed with the positive control treatments with 0.9% total P.