Abstract
Two very low birthweight infants with rickets are described; one had a low serum 25-hydroxy-vitamin D3 concentration. Similarities in their clinical courses included low birthweights, low calcium intakes, uncertain vitamin D intakes, and chronic administration of frusemide and sodium bicarbonate--all potential aetiological factors in the development of bone undermineralisation. Both infants had a resolution of their chronic lung disease before their treatment for rickets. This experience has led us to the more cautions use of frusemide and sodium bicarbonate in infants at risk for rickets, and shows the need to ensure daily vitamin D supplements.