This work has investigated the effect of echinacea extract on the weight of prostates in rats as well as on alterations of hystological structure and separate blood cells. This preparation was chosen for investigations due to its possible antiandrogenic effect and good immunostimulating features. Experiments were carried out with three-month old male Wistar rats, divided by six into three different groups. The first group was the control one. The rats of the second group were fed for 30 days with the usual food ration plus 50 mg/kg of echinacea extract. The third group was fed for 60 days in the same way as the second one. Clinical death of rats was caused by sodium phenobarbital, later a cervical dislocation was performed. After weighing the rats their prostates were removed and weighed. Patohystological investigations of the removed organs were carried out. Blood test for Shiling's analysis was taken. The weight of prostates in the first group of rats was 412.0+/-14.93 mg, in the second group - 403.0+/-13.33 mg, and in the third group it was 388.0+/-14.66 mg. Having calculated the proportion between prostates of rats and their body weight it was estimated that in the first group it made 0.125+/-0.009%, in the second group - 0.105+/-0.005%, and in the third group - 0.091+/-0.007%. The percentage of lymphocytes in the first group was 72+/-1.41; in the second group - 73+/-0.81; in the third group - 79+/-1,86. The percentage of segmented neutrophyle in the first group was 23+/-3.31; in the second group - 23+/-2.25; in the third group - 18+/-2.33. Having conducted analysis of the experimental results, a significantly important decrease of prostate weight of investigated rats, an increase in the number of lymphocyte as well as the alterations of hystological structures after using echinacea extract for eight weeks were observed.