Antibacterial activity of 1,1'-methandiylbis(2-methyl-1H-imidazole) (AIM) has been estimated both qualitatively and quantitatively against reference and clinical strains of Gram-positive and Gram-negative bacteria. MICs showed little variability among strains tested, ranging from 360 to 450 mu g/ml and indicating rather a moderate antibacterial activity. Inhibition of dehydrogenase activity was significant in Escherichia coli ATCC 25922 and followed closely time-kill dynamics. Although moderate, AIM proved also to be useful on the ability to successfully inhibit the growth of antibiotic resistant clinical strains.