In an attempt to locate biochemical markers specific for fetal distress we measured the amniotic concentrations of beta-endorphin, ACTH, cortisol, dopamine, norepinephrine and epinephrine with its major metabolite metanephrine (MN) in pregnancies with documented fetal well-being and pregnancies complicated by hypertension and fetal distress. While higher levels of cortisol and MN were found only in a selected subgroup of highly compromised subjects (p < 0.001 and p < 0.005, respectively), beta-endorphin increased significantly under conditions of moderate or severe intrauterine sufferance (p < 0.001 in both cases). Due to higher levels of the opioid even during the initial stage of fetal discomfort we evaluated its characteristics as a possible clinical marker. Specificity was 88.5%, whereas the sensitivity of 65.6% in the moderately compromised subgroup increased to 88.9% in severely suffering fetuses. Although more accurate and mainly real-time information on the fetal health status is obtained by means of biophysical methods, the determination of amniotic fluid beta-endorphin might be of clinical usefulness in prenatal diagnosis.