Ukrain is a semisynthetic drug with immunomodulatory properties derived from Chelidonium majus L. alkaloids and thiophosphoric acid. It acts selectively in a lytic way on cancer cells. Its protective properties have been shown in mice infected by influenza viruses. In this paper, the studies made on the estimation of the direct activity of Ukrain preparation on viruses and bacteria E. coli and S. aureus are described. Viruses of different haemagglutination titres were incubated with different concentrations of the preparation during period of 1, 2 and 24 h. Afterwards the samples were collected and used for the infection of the allantoic cavity obtained from 10-day-old hen embryos. A second method was based on the introduction of the Ukrain preparation into the allantoic cavity of embryos before infection with influenza viruses and after the infection of embryos. In both the described methods, the embryos were incubated within 48 hours. Then the presence of influenza viruses in allantoic fluid was estimated using a haemagglutination reaction with 30% hen blood cells. The influence of the preparation on hen embryo was also studied. In order to estimate the antibacterial activity the following procedure was used. To the preparation diluted with the growth medium from 500 micrograms/ml to 1 microgram/ml a definite amount of the bacteria S. aureus or E. coli was added, and after 24 and 48 h of incubation at 37 degrees C the results were read off. In the second method, the bacteria were added to 1, 10, 100 and 500 micrograms of the preparation in 1.0 ml of 0.85% NaCl, and after 1, 2 and 24 of incubation at room temperature the samples were collected and inoculated on solid Mueller-Hinton medium. The presence of bacterial growth or medium turbidity after 24 and 48 h of incubation was taken as a positive result. Our studies have revealed that the above mentioned preparation does not exert any negative influence on hen embryos that could make it difficult to estimate replication of influenza viruses. This preparation did not show any direct influence on the inactivation of influenza viruses and the bacteria E. coli and S. aureus.