Genetic mechanisms of macrolide resistance were investigated in six isolates of Ureaplasma spp. with erythromycin minimum inhibitory concentrations (MICs) ≥ 8 μg/mL that were derived from 370 cultures obtained over a several year period. Point mutations in domain V of 23S rRNA and/or mutations in ribosomal protein L4 genes are likely to be responsible for this drug resistance. Overall, macrolide resistance was uncommon, in contrast to tetracycline resistance that was documented in 121 unique isolates (33%). © 2011 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.