The results of assessing the possibilities of using of biomass of fallen leaves as a filler of composite polymer materials with a polyvinyl chloride polymer matrix are presented. Samples of composites with biomass of fallen leaves we obtained by extrusion and hot pressing method. The dependences of their physical and mechanical properties on the content of the filler were determined. These de-pendencies are given in the form of polynomial of the second degree. In terms of most physical and mechanical properties (with the exception of impact strength) composites with biomass of fallen leaves are superior to samples of wood-polymer composites with wood flour with a similar degree of filling. Made of a comparison of the effectiveness of three different plasticizers: dimethyl phthalate, dibutyl phthalate and dioctyl therephthalate. The most promising is the use of dibutyl phthalate as a plasticizer. It has been shown that the biomass of fallen leaves is an effective replacement for wood flour in the production of wood-polymer composite materials with a s fr.