Electrophoretic analysis of peroxidase isoenzymes and other proteins present in the culture medium of potato (Solatium tuberosum L. cv. Bintje) cells in suspension culture was carried out by isoelectric focusing and starch gel electrophoresis. The results showed that during the exponential growth phase, the number of peroxidase isoenzymes as well as their activities increased. In addition, several other proteins have increased in the culture medium. The high specific activity of medium peroxidase as compared to that of cellular peroxidase and differences in the release of various peroxidase isoenzymes suggest that the peroxidase was released by specific secretion.