Anti-microbial activity and pharmokinetics of erythromycin aspartate "Pharmachim" (EA) in chickens was studied. The investigations included erythromycin thiocyanat (ET) of the company Abbott-USA (the preparation Gallimycin poultry formula). The studies revealed that EA has an effect on Gram-positive microorganisms mainly. It is quickly resorbed by the digestive tract and following the administration of 50 and 100 mg/kg body weight (applied by tube) in doses of 0.14 to 0.8 meg/cm3 it can be detected in the blood serum of chickens after 10 min only have elapsed. Maximal concentrations (from 0.35 to 0.95 meg/cm3) are discovered at about the 30-60th min and after that EA levels are gradually reduced to traces or 0.125 mcg/cm3 by 24th h. Application via drinking water in a dose of 115 mg/l results in EA quantities of 0.11 to 0.2 meg/cm3 detected in the blood during the entire course of treatment with therapeutic water. The use of equal ET doses results in 20 to 39% lower antibiotic levels. The same is true for EA and ET content in organs and tissues. Both preparations are eliminated by the bile secretion untill the 96th h post treatment's end. Resorption of EA is quick and high grade following muscular injection and at a dose of 20 mg/kg body weight the antibiotic persists in bacteriostatic concentrations in the blood up to the 15th, while at a dose of 40 mg/kg body weight-up to the 24th h post its single application.