The purpose of this study was to exclude the potential antimicrobial activity of certain analgesic active imidazo[2,1-c][1,2,4]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 central nervous system of tested animals, correlated with relatively low acute toxicity values (LD50 in range from 1100 to 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][1,2,4]triazines in concentrations of 100 microg ml(-1) and 200 microg ml(-1) had no influence on the growth of microorganisms tested. Lack of this influence can be profitable in the case of analgesic active compounds.