ABSTRACT Background: The science of identification and employment of medicinal plants dates back to the early days of man on earth. Cannabis (hashish) is the most common illegal substance used in the United States and was subjected to extensive research as a powerful local disinfecting agent for mouth cavity and skin and an anti-tubercular agent in 1950. Methods: Clinical strains were isolated from hospitalized patients in Vali-e-Asr Hospital of Arak. The hydro-alcoholic extract of cannabis (5 g) was prepared following liquid- liquid method and drying in 45˚C. The antimicrobial properties of the extract were determined through disk diffusion and determination of MIC (Minimum Inhibitory Concentration). Results: First, the sensitivity of bacteria was detected based on disk diffusion method and the zone of inhibition was obtained for MRSA (12 mm), S.aureus 25923 (14 mm), E. coli ESBL+: (10 mm), and Klebsiella pneumoniae (7 mm). Disk diffusion for Pseudomonas and Acinetobacter demonstrated no inhibitory zones. Through Broth dilution method, MIC of cannabis extract on the bacteria was determined: E.coli 25922: 50µg/ml, E.coli ESBL+:100 µg/ml, S.aureus 25923:25 µg/ml, MRSA: 50 µg/ml, Pseudomona aeroginosaESBL+> 100 µg/ml, Pseudomonas: 100 µg/ml, Klebsiella pneumoniae: 100 µg/ml, and Acinetobacter baumannii> 1000. Conclusion: The maximum anti-microbial effect of the hydro-alcoholic extract of cannabis was seen for gram positive cocci, especially S. aureus, whereas non- fermentative gram negatives presented resistance to the extract. This extract had intermediate effect on Enterobacteriacae family. Cannabis components extracted through chemical analysis can perhaps be effective in .treatment of nosocomial infections Hossein Sarmadyan, Hassan Solhi, Tahereh Hajimir, Negin Najarian-Araghi, Ehsanollah Ghaznavi-Rad