Abstract: Organotin compounds have shown a wide spectrum of biological effects and have been extensively studied as fungicides, bactericides, acaricides and wood preservative. A large number of papers have reported the use of organotin compounds as bacterial growth inhibitors. The biocide activity of tribenzyl- and dibenzyltin compounds has been informed, but the effect that the methoxyl group in the aromatic ring could have on the activity of the compounds has not been reported in previous literature. For that reason, we performed an in vitro qualitative assay, and evaluated the activity of benzyltri-n-butyltin (I) and 3,5-dimethoxybenzyltri-n-butyltin (II) against the growth of two bacterial strains: Staphylococcus aureus (Gram-positive) and Escherichia Coli (Gram-negative), using agar well diffusion method. In all cases Merck Art 5273 broth was employed. THF was used both as the solvent of choice for the organometallic compound (since the organotin compounds are not water soluble) and as a negative control. Different concentrations I and II were prepared and the activity was determined by measuring the diameter of the inhibition zone (in cm). The results proved not only that the Gram-positive strain is more susceptible to the inhibition growth effect of the organotin compounds evaluated, but also that 3,5-dimethoxybenzyltri-n-butyltin has higher antibacterial activity. According to this preliminary results we conclude that the presence of the methoxyl group in the aromatic ring would enhance the antibacterial activity of the organotin compound tested here.