Studies were carried out on the degradation of polyethylene package film with 5% of starch (MALEN E FABS 23 DO 22), which was exposed to UV rays (low pressure mercury lamps Philips UV-A TL/05, 15 W power, emission maximum 365 nm) and soil microorganisms. Film of the 0,04-0,1 mm thickness film was exposed to UV radiation for 60 h, 120 h, 180 h, 240 h, 300 h and 800 h. The exposed film was stripped up into 150 mm x 15 mm pieces and underwent the soil burial test for 24 weeks in the temp, of 28-30°C and relative humidity of 20-30%. The degradation was estimated based on the tensile strength. The impact of the UV-radiation exposure time and soil microorganisms on the mechanical properties of the polyethylene film with starch were analysed by the regression models. The 3-rd order polynomial model was fitted to empirical data. The tensile strength was turned out to be useful measure of the mechanical changes in the polyethylene film.