The antimicrobial activity of several extracts and fractions of some Hypericum species (H. rupestre Jaub. & Spach, H. vacciniifolium Hayek & Siehe and H. imbricatum Poulter) was investigated using the disc diffusion method against Escherichia coli ATCC 11230, Staphylococcus aureus ATCC 6538P, Klebsiella pneumoniae UC57, Micrococcus luteus La 2971, Bordetella bronchiseptica ATCC 19395, Proteus vulgaris ATCC 8427, Pseudomonas aeruginosa ATCC 27853, Corynebacterium xerosis CCM 7064, Mycobacterium smegmatis CCM 2067, Bacillus subtilis ATCC 6633, Aeromonas hydrophila ATCC 49803, Candida albicans ATCC 10231, Saccharomyces cerevisiae ATCC 9730, Kluyveromyces fragilis NRRL 2415 and Rhodotorula rubra CCY. The methanol extract and chloroform fraction of H. vacciniifolium, as well as the methanol extracts, butanol and chloroform fractions of both H. rupestre and H. imbricatum, showed good antimicrobial activity against especially Gram-positive bacteria and the Gram-negative bacterium Bordetella bronchiseptica. The methanol extracts and fractions did not have antifungal activity. The results of the study support the use of these specimens in Turkish traditional medicine to treat skin and eye infections.