Recent advances in forensic science in the identification of human seminal acid phosphatase are presented, with particular attention to the acrylamide gel electrophoretic method. In that method a difficulty in distinguishing seminal acid phosphatase from certain fecal phosphatases has been observed and an attempt is made here to distinguish the phosphatases from one another experimentally by differential substrate specificity. 4-Methylumbelliferyl phosphate and alpha-naphthyl acid phosphate are used as reaction substrates. Although seminal and vaginal acid phosphatases are differentiated by the modified method, fecal phosphatase is not clearly differentiated from seminal acid phosphatase.