The incidence of Mycoplasma hominis (M. hominis) y Ureaplasma urealyticum (U. urealyticum) was investigated in 113 endocervical samples obtained from women who were seen for different gynecological pathologies. Forty-seven (42%) patients were positive to these microorganisms; 26 cases (23%) were positive for M. hominis and 21 (19%; p = NS) for U. urealyticum. Average age was 32.1 +/- 7.7 years; the average number of sexual partners was 1.7 +/- 1.1. Eleven of 17 patients with 3 o more sexual partners were positive for Genital Mycoplasma (GM), and U. urealyticum was found more often in this group. A higher incidence of GM was found in women between 26 and 30 years (34%); 57.5% of the patients with positive cultures for GM had begun sexual activity before 20 years of age. M. Hominis was found in 61% of women with no parity and U. urealyticum in 71% of parous women. The cultures were positive in 10 of 14 patients with pelvic inflammatory diseases (PID). A cervical biopsy was taken from 52 cases and the diagnosis of cervical intraepithelial neoplasia (CIN) was made in 49 (94%) but only 24 of them were positive for GM (50%). Thirty-five patients suffered sterility, and 12 (34%) were positive for GM, however all positive cases consulted because of primary sterility. The conclusions obtained from this study are: 1) Near half of the patients was positive for GM and none of the species was predominant over the other. 2) The more sexual partners the higher was the incidence of GM, especially U. Urealyticum. 3) The lower the age of the first sexual intercourse the higher the probability of contamination with these microorganisms. 4) M. hominis was more common in nulliparous women and U. urealyticum was found more often in parous patients; the number of deliveries did not have influence in these findings. 5) A statistical significance between GM and PID was found (p = 0.03). 6) GM have no influence on spontaneous abortion. 7) No statistical significance was found between GM and the beginning and evolution of CIN. 8) No relation statistically significative was found between GM and sterility.