We evaluated the clinical usefulness of measuring the serum concentrations of human chorionic gonadotrophin (HCG) and progesterone to distinguish between early viable and nonviable pregnancies. We investigated 110 women with clinical symptoms of abnormal pregnancy. A single HCG measurement did not clearly distinguish between ectopic and failing intrauterine pregnancies; an HCG value below 3,000 IU/L, together with a serum progesterone below 40 nmol/L, predicted abnormal pregnancy outcome in 97% of women (positive predictive value: 91%; negative predictive value: 95%). Serum HCG value above 3,000 IU/L or progesterones above 40 nmol/L, discriminated between an ongoing pregnancy and an abnormal pregnancy in 87% women (positive predictive value: 95%; negative predictive value: 91%) and provided reassurance of an ongoing pregnancy. Our results suggest that a combination of serum progesterone and HCG measurements provide clinically useful biochemical information which enhances the prediction of pregnancy outcome.