Peculiarities of growth of the strains of two species of microscopic fungi Aspergillus versicolor and Paecilomyces lilacinus were analyzed under exposure to chronic irradiation. It was shown that the rate of radial growth increased nonuniformly in the range of doses from 0 to 250 mGy but with maximums at a certain dose of radiation. It was shown that the absorbed dose of radiation to 2 Gy did not influence the survival of investigated strains in comparison with the control ones without irradiation. It was shown that the doses of irradiation to 2 Gy (at capacity exposure dose 0.955 microC/kg) are small for these species of microscopic fungi.