Genetic control of exocellular acid phosphatase of yeast Saccharomyces cerevisiae (acph 2) is studied. 64 mutants with the impaired activity of acid phosphatase have been obtained by UV-irradiation. All the mutations have been distributed among 4 genes: ACP1, ACP2, ACP3, ACP4 using functional and recombinational tests for allelism. It is shown that mutations in genes ACP1--ACP3 are recessive, but in the gene ACP4--dominant. The gene ACP4 is found to be located 0.41+/-0.064 in strains from centromere and to have no linkage with ACP1. Possible functions of genes studied are under discussion.