The photodynamic activity of 5,10,15,20-tetrakis (4-N-methylpyrydyl) porphyrin, its nikel and zinc complexes toward Candida albicans and Rhodotorula bogoriensis was studied. It was found that molecule structure peculiarities of the compounds correlate with the level of cell photoinactivation. The second day biomass increase of test cultures as compared with the first one can be used as an analogue of the tumor growth stimulation by ineffective doses of chemotherapeutic medications.