purpose: to analyze the antimicrobial properties of silicon oil (óleo de silicone？, ophthalmos, brazil) on in vitro bacterial growth of different microorganisms related to endophthalmitis. methods: the following microorganisms were analyzed: (1) pseudomonas aeruginosa (atcc 27583); (2) escherichia coli (atcc 25922); (3) staphylococcus aureus (atcc 25923); (4) staphylococcus epidermidis (atcc 12228); (5) candida albicans (atcc 10231); (6) klebsiella pneumoniae (atcc 13883); and (7) streptococcus pneumoniae (atcc 49619). the plates were incubated at 35 ± 2oc and its growth examined after 24 hours. an empty disk was placed in the center of each plate as a control. results: no inhibition halos were verified in any of the plates containing the four different concentrations of the bacterial inocula. conclusions: the silicon oil 1000 cps does not have any effect on bacterial growth of any of the studied microrganisms.