Restriction fragment length polymorphism (RFLP) analysis of the PCR-amplified proximal region of the gene encoding cytadherence accessory protein P110 (MG192) revealed DNA sequence divergences among 54 Mycoplasma genitalium clinical strains isolated from the genitourinary tracts of women attending a sexually transmitted disease-related health clinic, plus one from the respiratory tract and one from synovial fluid. Seven of 56 (12.5%) strains exhibited RFLPs following digestion of the proximal region with restriction endonuclease MboI or RsaI, or both. No sequence variability was detected in the distal portion of the gene.