Introduction: The use of medicinal plants to treat infections is an old method, having antimicrobial properties that can be common problems in the use of antibiotics to restore. Thus the aim of this study, anti-bacterial effects of essential oils of rosemary plant was on five different bacteria in vitro. Essential oil samples after drying in the shade plant, using steam distillation and were isolated using distillation.

Materials & methods: An antibacterial effect of this plant by successive dilution and disk diffusion methods was evaluated. In order to control and standardized methods of antibiotic discs and standard bacterial strains were used.

Findings: Based on the results, P. mirabilis and E.fecalis the most sensitive and most resistant bacteria to the dilution ratio of 1, ½ and ¼ were essential but the most sensitive E.fecalis and E.coli bacteria to dilution of 1/8 , 1/16, 1/32 and 1/64 had. The evaluation results o disk diffusion method with antibiotic disks, the effect of the plant compared with Gentamicin disks and streptomycin,  showed against five strains of S.aureus ATCC1885, S.epidermidis ATCC2405, E.fecalis QTCC2321, E.coli ATCC1652, and P.mirabilis ATCC 2601.

Discussion & Conclusions: The results of this study show that plant oils can replace for chemical drugs to treat infections. Of course all of this oil should be carefully evaluated in vivo and in vitro.