The widespread use of testicular hyaluronidase preparations determines the particular interest in the development of oral dosage form. The drug under development, which is hyaluronidase pegylated using electron beam immobilization technology (PEG-GIAL), requires an assessment of its safety. Identification of possible neurotoxic action, as well as the influence on cardiac function seems to be very relevant. Aim of the study was to investigate the effect of PEG- GIAL on behavioural reactions and electrical activity of the heart of experimental animals. Material and methods. Eight hundred of white outbred rats (male and female) were used as experimental animals. The effect of PEG-GIAL on the central nervous system was determined using the «open field with holes» test, examining such characteristics as emotional reactions and orientation-research behaviour. The functional state of the cardiovascular system was assessed by electrocardiography data. Results. PEG-GIAL administration in all studied doses does not lead to changes in the functional activity of CNS, does not have a pronounced effect on the indices of orientation-research behaviour and emotional reactions in laboratory animals. No statistically significant changes in the cardiogram of rats were revealed, including no intersex differences. Conclusions. PEG-GIAL administration in all studied doses has no toxic effect on the electrical activity of the heart and has no pronounced effect on changes in the functional activity of the CNS and behavioural reactions.