Organic and aqueous solvent extracts and fractions of Micromeria nervosa (Desf.) Benth. (Labiatae) were investigated for antimicrobial activities on several microorganisms including bacteria and yeast. The different extracts differed significantly in their antimicrobial activities with the ethanolic extract being most active, followed by ethyl acetate and petroleum ether extracts. The least active extract was the aqueous. No significant difference between the different test microorganisms in their susceptibility to different extracts, with Candida albicans being the most susceptible to ethanolic extract giving 1.5 times the effect of nystatin. One of the main active ingredients of M. nervosa was isolated and identified as carvacrol. No significant difference in antimicrobial activity was found between carvacrol and its isomer thymol. The most susceptible test microorganism was Proteus vulgaris to carvacrol, and P. vulgaris and C. albicans to thymol. The least susceptible bacterium to both fractions was Pseudomonas aeruginosa. Minimum inhibitory concentration (MIC) and minimum bactericidal or fungicidal concentrations (MBC or MFC) were determined for both compounds.