Two cases with vitamin D-deficient osteomalacia of digestive origin (coeliac disease) have been treated orally with 1,25(OH)2D3 in dosages of respectively 8 and 3 microgram/24 h. Serial transiliac bone biopsies have been performed. Mineralization fronts were normalized after respectively 4 and 1.5 months, whereas mineralization rates, as demonstrated by double tetracycline labeling, were normalized respectively after 2 and 1.5 months. In both cases osteomalacia healed completely despite persistently low 25(OH)D levels in the serum. It is obvious from these studies that 1,25(OH)2D3 per se is able to cure vitamin D-deficient osteomalacia, a finding that has been disputed. Whether 25(OH)D acts more rapidly on bone, as suggested by the studies performed in one case with anticonvulsant osteomalacia, remains to be proven.