The article is devoted to the analysis of the plastics biodegradation rate under the impact of micromycetes. Three types of widespread soil micromycetes were selected for the experiments. The strains of thermotolerant micromycetes (optimum growth at a temperature of 12-25°C) isolated from karst caves were used. Penicillium chrysogenum, was highlighted with gypsum sinter deposits of the Novoafonskaya cave named after G. Sh. Smyr (Abkhazia). P. nigrum, was isolated from clay deposits of Divya cave (Russia, Perm region). Sporotrichum sp. was allocated from the clay deposits of the cave Mchishta-Akshasha (Abkhazia). Four types of plastics were biodegraded: high-pressure polyethylene, polypropylene, polyethylene terephthalate, low-pressure polyethylene. The experiments were carried out in the Chapek-Dox nutrient medium in liquid and agar medium. Evaluation of the biodegradation rate was carried out by calculating the mass loss of samples. Qualitative changes in the surface were studied by using scanning electron microscopy. It was found that P. chrysogenum had the highest rate of biodegradation and P. nigrum had the lowest rate. The weight loss was the reatest in polyethylene terephthalate, lower - in polypropylene, and the lowest one - in the low-pressure polyethylene. © 2019 Published under licence by IOP Publishing Ltd.