An activity of unspecific acid phosphatases (I and II) was found in the culture medium during the growth of yeast. These phosphatases differed in a number of physicochemical properties. Addition of inorganic phosphate to the medium inhibited the synthesis of phosphatase II, but not of phosphatase I. Moreover, there was a mutual regulation of the enzymes. Mutations in three genes (pho₁, pho₂ and pho₃) altered the activity of acid phosphatase I, but only the mutation in pho₁ gene caused a complete disappearance of the enzyme activity. Acid phosphatase II was under the control of asp₁ gene. An increase of temperature in the medium leads to decrease in the activity of phosphatases. (18 references.)