We have purified two forms of Zn²⁺-dependent acid phosphatase (Zn²⁺-APase) from bovine liver, both of which require Zn²⁺ to hydrolyze the substrate p-nitrophenyl phosphate in an acidic environment. The apparent molecular weights of these two forms of Zn²⁺-APase were estimated to be about 100000 and 62000 by gel filtration, and about 44000 and 31000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, respectively. The low-molecular weight (LMW) Zn²⁺-APase catalyzed the hydrolysis of myo-inositol-1-phosphate in the presence of 3 mM Mg²⁺ at physiological pH, but the high-molecular weight (HMW) enzyme did not. The LMW-Zn²⁺-APase of bovine liver was recognized by polyclonal antibodies developed against the Zn²⁺-APase of bovine brain, but the HMW-Zn²⁺-APase was not.