Sertralin is a psychotropic drug which acts by inhibiting the selective serotonin re-uptake in the synaptic area. Previous studies have shown that some antidepressant agents have antibacterial activity. The aim of this study was to investigate the in vitro antibacterial activity of sertralin. A total of 224 bacterial strains isolated from clinical specimens together with standard control strains were included to the study. The antibacterial activity of sertralin was determined by microdilution method in Mueller-Hinton broth according to the Clinical and Laboratory Standards Institute (CLSI) guideline. The minimum inhibitory concentration (MIC) values were found to be 4-32 microg/ml for 22 methicillin-susceptible Staphylococcus aureus strains, 16-32 microg/ml for 25 methicillin-resistant S. aureus strains, 8-32 microg/ml for 20 methicillin-resistant coagulase-negative staphylococci strains, 16-32 microg/ml for 4 vancomycin-susceptible Enterococcus faecalis strains, 0.5-32 microg/ml for 10 vancomycin-susceptible Enterococcus faecium strains, 2-8 microg/ml for 12 vancomycin-resistant E. faecium strains, 16-128 microg/ml for 21 Acinetobacter baumannii strains, 4->128 microg/ml for 20 Klebsiella pneumoniae strains, 0.25-128 microg/ml for 24 Escherichia coil strains, 64->128 microg/ml for 22 Pseudomonas aeruginosa strains, 128->128 microg/ml for 2 Proteus vulgaris strains, 64->128 microg/ml for 8 Proteus mirabilis strains, 32->128 microg/ml for 7 Stenotrophomonas maltophilia strains, 32-128 microg/ml for 21 Enterobacter cloacae strains and 8-128 microg/ml for 6 Enterobacter aerogenes strains. The MIC values of sertralin against standard strains were as follows; 16 microg/ml for S. aureus ATCC 29213 (methicillin-susceptible), 32 microg/ml for S. aureus ATCC 43300 (methicillin-resistant), 16 microg/ml for E. faecalis ATCC 29212, 32 microg/ml for K. pneumoniae ATCC 700603, 32 microg/ml for E. coli ATCC 25922 and > 128 microg/ml for P. aeruginosa ATCC 27853. Sertralin has showed antibacterial activity mainly against gram-positive bacteria, and it was surprising that MIC values of vancomycin-resistant enterococci were lower than those of vancomycin-susceptible ones. Further in vivo and in vitro studies are required to provide reliable data about the use of sertralin as an adjuvant agent in the antibacterial treatment of infections caused by multidrug-resistant bacteria.