The susceptibility of 67 isolated Ureaplasma urealyticum, 25 Mycoplasma hominis and five Mycoplasma spp. reference strains to fleroxacin, ofloxacin, josamycin and doxycycline was determined by agar dilution. Josamycin had the best activity against Ureaplasma urealyticum, followed in order by doxycycline, ofloxacin and fleroxacin. All the strains were inhibited by josamycin at 0.4 mg/l, while only 38.8% of the strains were inhibited by doxycycline at this concentration. Mycoplasma hominis strains were more susceptible to doxycycline, ofloxacin and fleroxacin than were Ureaplasma urealyticum strains. Here, doxycycline had the best activity followed by ofloxacin, josamycin and fleroxacin. Notably, three Ureaplasma urealyticum strains and one Mycoplasma hominis strain were not inhibited by 6.4 mg/l doxycycline.