The acrylic copolymers are among the most important polymeric materials, their main destination being the manufacturing of acrylic fibers for the textiles industry. After usage, acrylic fibers represent a pollution source, mainly for the soil. Nowadays there are no specific information concerning the interaction between these polymers and the soil microorganisms, and that’s why our interest in the topic. In this paper we have studied the effect of polyacrylonitrile (PAN) upon the development of different soil microorganisms. Soil samples have been extracted, mixed in various ratios with PAN powder, and returned into the natural environment. After two years, complex chemical and biological analyses have been bperformed on the samples [1]. A first observed effect was the increasing of bvthe mycosis and bacterial colonies number. The more polymer quantity, the bmore increase of colonies. In the same time, a reduction of the number of bmicroorganism species has been observed. These phenomena led us to the conclusion that there are important interactions between soil microorganisms and the synthetic polymers. Several changes of the polymers have been also observed.