Progesterone (P), estradiol (E2), relaxin, CA-125, Schwangerschaft protein, and human chorionic gonadotropin (hCG) were measured in 221 pregnancies (less than or equal to 77 days gestation). The cohort was divided into asymptomatic subjects (group I, n = 117) and those with threatening symptoms (group II, n = 104). Outcome was ascertained as viable (normal at 14 weeks, n = 131), spontaneous abortion (n = 58), or ectopic gestation (n = 32). Statistical analysis revealed no differences in the mean maternal or gestational ages among the viable pregnancies, abortions, and ectopics in group I and group II. In group I, significant differences in the means were noted for P, hCG, relaxin, and CA-125 among those destined to abort, compared with those who were not. In group II, differences were noted in P, hCG, relaxin, and E2 when viable and nonviable pregnancies were compared. Within group II, there were significant differences between the means of E2 and CA-125 when the aborters were contrasted with ectopics. Receiver operating characteristic curve analysis revealed that P was the single most reliable predictor and was most effective in threatened pregnancies. Stepwise logistic regression of the six markers in group II provided an equation of possible clinical utility in differentiating abortion versus ectopic pregnancy in threatened gestations based on CA-125 and E2 levels.