Maternal serum alpha-fetoprotein (MSAFP) was determined in patients 33 to 40 weeks pregnant, and the Iesults were analysed with consideration of the presence and quality of hypertensive disease that complicated many of the pregnancies. Patients with incompletely controlled hypertension had significantly higher MSAFP levels than control patients with pregnancies uncomplicated by any risk factor. MSAFP elevation was greatest in pre-eclampsia (301.6 k 147.6 kU/L, n = 35) >chronic hypertension with superimposed pre-eclampsia (240.4 f 74.7 kU/L, n = 30) > chronic hypertension (204.1 f 105.3 kU/L, n = 141). Each was significantly increased (P< 0.0001) over control pregnant patients' levels (104.3 f 38.8, n= 187). At each gestational week from 33 weeks to term, MSAFP of combined hypertensive women was significantly greater than corresponding control levels (P < 0.003 to < 0-Oool).The magnitude and time of onset of MSAFP increase may indicate severe fetal distress.