There is increasing evidence showing the association between maternal genital infection, prematurity and neonatal or maternal morbidity. To know the genital flora of women attending a high risk pregnancy service, 73 consecutive pregnant women attending the high risk pregnancy service at the Hospital San Borja-Arriarán from may to august 1992 were included in this study, 75.3% of the vaginal discharges corresponded to fluids of normal appearance and 24.7% were altered. The microorganisms most frequently isolates were lactobacilli, U. urealitycum and coagulase negative strains of Staphylococcus. The Gram stain revealed the existence of bacterial vaginosis in 20.9% of the vaginal smears. There was a significant higher incidence of lactobacilli in patients with balanced healthy vaginal flora, whereas Gardnerella vaginalis and Mycoplasma hominis were isolated significantly more frequently from women with bacterial vaginosis. With the exception of genital mycoplasma, it was found a low incidence of sex transmitted bacteria in this study.