The two thyme (Thymus vulgaris L. and Thymus serpyllum L.) and three oregano (Origanum vulgare L., Origanum onites L. and Origanum majorana L.) hydrosols, widely used in food products and as drinks, were tested for their inhibitory effects against four pathogenic bacteria (Escherichia coli ATCC 25922, E. coli O157:H7 ATCC 33150, Staphylococcus aureus ATCC 2392 and Yersinia enterocolitica ATCC 1501). Two principles were used in determining the antibacterial effects of spice hydrosols: inhibition zones were determined by paper disc diffusion method, and the bacteriostatic effects, bactericidal effects and the growth inhibition levels were studied as colony forming units (cfu) in broth cultures. All tested bacteria were inhibited by all of the spice hydrosols using paper disc diffusion method. According to serial dilution method, while all spice hydrosols at 10 and 25 mL/100 mL concentrations had generally bacteriostatic activities, the same hydrosols appeared to have bactericidal effects at concentrations above 50 mL/100 mL. The most sensitive of the bacteria against the spice hydrosols was S. aureus. In addition, the most inhibitive of the spice hydrosols on the four pathogenic bacteria were O. onites L. and O. majorana L. (C) 2003 Swiss Society of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved.