The HuIFNA16, HuIFNB1, and BoIFNG genes encoding human alpha 16, beta-interferons and bovine gamma-interferon were cloned under the control of the yeast Pichia pastoris AOX1 gene promoter. The yeast strains producing heterologous interferons intracellularly and extracellularly were constructed. There was no effect of high level of heterologous protein synthesis on the yeast P. pastoris cell growth, unlike yeast Saccharomyces cerevisiae. The considerable part of the heterologous interferons was detected in the yeast P. pastoris soluble protein fraction but not in the "inclusion bodies." The treatment of human beta-interferon with endoglycosidase H showed that protein was expressed in glycosylated and unglycosylated forms. On the strength of these data, the hypothesis was suggested that the more effective heterologous gene expression in yeast P. pastoris and enhanced resistance of the methylotrophic yeast to negative effects of recombinant proteins was due to the special features of its metabolism.