Phenomena of melanization of radioactively polluted soils, due to prevalence of melanin-containing species and positive radiotropism of some micromycetes have been found during monitoring of mycobiota of the 30-km alienation zone of the Chernobyl NPP for 10 years. To elucidate the contribution of the melanin system to the cell protection against irradiation, the influence of gamma-irradiation on the activity of protein synthesis in four Cladosporium cladosporioides (Fres.) de Vries strains has been investigated. Two strains isolated from radioactively polluted substrates were characterised by the presence of positive radiotropism. Laboratory strain 396 and its alb-mutant (with blocked melanin synthesis), did not possess this feature. The protein synthesizing activity was assayed by incorporation of 14C-leucine in the protein fraction of mycelium, grown during 7 days under continuous gamma-irradiation of low intensity and without it. The protein synthesis was activated in the radioactively treated mycelium of dark-pigmented C. cladosporioides strains and it was suppressed in similarly treated mycelium of alb-mutant of C. cladosporioides. The rate of 14C-leucine incorporation into biomass of investigated strains correlated with positive radiotropism. The dependence between protein synthesis intensity and the availability of melanin protection system in micromycetes is assumed.