The cervicovaginal and endometrial isolation rates of Ureaplasma urealyticum and Mycoplasma hominis and relevant demographic data were obtained at the time of laparoscopy in 193 women from infertile marriage. For comparative purposes, fertile women undergoing laparoscopy for tubal ligation (n = 56) or other purposes (n = 64) were also cultured. Blacks were more likely than caucasians to be infected with either organism in all population types (p ≤ .05); however, no differences were noted in cervicovaginal carriage rates for blacks in different patient populations. M. hominis was isolated more frequently from tubal reanastomosis patients and less often from infertile patients, p≤ .001. No differences were noted among the infertile subpopulations. Although the isolation rate of U. urealyticum from the different patient populations was similar, one subpopulation within the infertile population (male factor) was identified in which the prevalence of ureaplasmal infection of the female's lower genital tract was over twice as high (p≤ .005) as in other infertile women. Yet there were no statistically significant differences in the demographic data of this subpopulation as compared to the population of infertile women as a whole. No other clinical subpopulation with single or multiple diagnoses not including male factor had an increased prevalence of infection. Eighty percent of infected, infertile couples had no clinical evidence of male factor infertility, indicating that only certain individuals are affected. This possibly explains why previous studies involving small numbers of patients without regard to clinical subpopulations have failed to show significant differences between infected and uninfected couples. Neither mycoplasmas, other bacteria, chlamydiae, toxoplasmas, nor viruses were significantly isolated from the endometrium in any population.