The purpose of this study was to exclude the potential antimicrobial activity of certain analgesic active imidazo[2,1-c]triazines. These compounds contain in their chemical structure potential pharmacophore formations and features similar to those present in morphine - like analgesics and opioid receptor agonists containing no basic nitrogen atom. These compounds showed significant antinociceptive activity on the central nervous system of the tested animals, correlated with very low toxicity value (LD50 value of above 2000 mg kg(-1) b.w. via i. p.). Microbiological tests were conducted on 106 strains of bacteria, 6 strains of yeast-like fungi and 3 strains of moulds. The examined imidazo[2,1-c]triazines in concentrations of 100 microg ml(-1) and 200 microg ml(-1) had no influence on the growth of the microorganisms tested. Lack of this influence can be profitable in the case of analgesic active compounds.