Serum chemistry studies and radiological examination of the lamina dura and phalanges were conducted in 50 pregnant women, 25 of whom had been administered calcium and vitamin D supplements during the 3rd trimester. The non-supplemented pregnant women showed significant hypocalcaemia, elevated serum heat-labile alkaline phosphatase activity, and resorption of the lamina dura. The supplemented group of pregnant women also showed resorption of the lamina dura, although the serum chemistry was essentially normal. It is suggested that, probably because of gestational hyperparathyroidism, mild resorption of the lamina dura may be a feature of normal pregnancy.