Ureaplasma parvum colonises human mucosal surfaces, primarily in the urogenital and respiratory tracts, causing a wide spectrum of diseases, from non-gonococcal urethritis to pneumonitis in immunocompromised hosts. Although the basis for these diverse clinical outcomes is not yet understood, it has been suggested that only certain strains of these micro-organisms are disease-associated. The aim of this study was to determine the distribution of Ureaplasma biovars and U. parvum serovars and to estimate their possible association with age, absence of lactobacilli, clinical symptoms and antibiotic resistance. DNA was extracted by endocervical, vaginal and urethral samples obtained from 158 women positive for U. urealyticum by culture and were biotyped by polymerase chain reaction (PCR) targeting the multiple-banded gene. Parvo biovar (biovar 1) was found in 136 (86%) and T960 biovar (biovar 2) in 22 (14%) patients. Among the different serovars of U. parvum, we found that serovar 3/14 was present maximally in the 21-25-year-old age group, while T960 biovar was distributed with quite similar frequency in women of 26-30 and >40 years of age. In this study, U. parvum serovar 3/14 and T960 biovar were found to be significantly associated with symptomatic patients and a loss of lactobacilli, while, on the contrary, U. parvum serovar 6 was significantly correlated with asymptomatic women and normal vaginal flora. The most active antibiotic for the majority of Ureaplasma isolates was tetracycline. These preliminary data show the possibility of distinguishing between the more or less virulent strains of Ureaplasma, with important consequences for therapeutic treatment.