Pregnancy-associated plasma protein-A (PAPP-A), a macromolecular glycoprotein of placenta] origin, was reported to be depressed in established ectopic pregnancies. CA 125 is a known marker for ovarian cancer found to be elevated during the first trimester of pregnancy and in women with pelvic inflammatory disease. The present study investigated the usefulness of these parameters to predict the outcome of pregnancy in asymptomatic patients with a positive pregnancy test after in-vitro fertilization and embryo transfer (IVF-ET). Blood samples (n = 159) were obtained at different periods of time post-ET from 39 women, 21 of whom experienced a normal pregnancy, 12 had an intrauterine abortion and six had an ectopic pregnancy. PAPP-A and CA 125 were measured by radioimmunoassays. From day 30 onwards in normal pregnancies, PAPP-A was significantly increased over non-pregnant controls. In the spontaneous abortion group, the levels of PAPP-A were significantly lower than in normal pregnancy but higher than in non-pregnant controls. In ectopic pregnancy, PAPP-A remained at the level of nonpregnant controls throughout the entire observation period. CA 125 was significantly increased in all types of pregancy. However, in two cases of hyperstimulation followed by a normal pregancy and in four cases of ectopic pregnancy with signs of peritoneal irritation (hydrosalpinx, ruptured ectopic or salpingitis) the levels of CA 125 were 15-50 times higher than in normal pregnancies. PAPP-A levels < 10th percentile, measured after 30 days post-ET, were an excellent diagnostic parameter for ectopic pregnancy or intrauterine abortion with a sensitivity of 87.5% and a predictive value of disease of 100%. In contrast, CA 125 determinations had no diagnostic value and were only indicative of peritoneal inflammation in either normal or pathological pregnancies. It is concluded that PAPP-A is a good parameter by which to monitor postimplantation viability of embryos in FVF-ET patients.