In a patient with rickets developed after bowel surgery, we found a low serum concentration of 25-OHD and normal serum concentration of 1, 25-(OH)₂D. Oral administration of la-OHD₃ resulted in dramatic improvement of rickets and normalization of serum 25-OHD and calcium. These findings suggest that 25-OHD deficiency may play an important part in the pathogenesis of osteomalacia.