Semen specimens from 24 donors in an artificial insemination program--selected for women whose infertile status was determined to be male factor-related and for whom no female factor could be determined--were cultured for the presence of Ureaplasma urealyticum. A life table statistical analysis indicated that conception did not occur sooner in the U. urealyticum-negative group (n = 14) compared with those women inseminated with the U. urealyticum-containing semen (n = 10). In addition, no significant differences were detected in semen analysis count, grade, or motility between semen with or without U. urealyticum. We found no differences in the occurrence of fetal morbidity or mortality in ten conceptions between the women impregnated with Ureaplasma-positive (n = 14) and Ureaplasma-negative (n = 6) semen. Thus, our study does not support the role of U. urealyticum as a cause of male factor-related infertility or early pregnancy loss.