A calcium absorption investigation was carried out with the purpose of determining whether lactose-hydrolyzed milk facilitates calcium absorption in subjects with lactose malabsorption. Nine children participated in the study, which was divided into two investigation periods separated by at least 1 week. During the first period the children were given a lactose-free diet, whereas during the second period their diet contained lactose-hydrolyzed milk. The amount of calcium, number of calories, and rotation of specifically defined meals in the diet during the two periods were identical, and the children functioned as their own controls. We found calcium absorption to be significantly higher with the diet containing hydrolyzed milk than with the lactose-free diet supplemented with extra calcium (p less than 0.05). During the study a double-blind lactose intolerance test was performed. The children had significantly fewer clinical symptoms and signs, such as abdominal pain, borborygmus, meteorism, and defecations, within 24 h after drinking 0.5 L of lactose-hydrolyzed milk as compared with drinking ordinary milk (25 g of lactose). None of the children experienced any unpleasant side effects when consuming the lactose-hydrolyzed milk (approximately 94% degree of hydrolysis) during the study period. All the children liked the hydrolyzed milk because it had a pleasant, sweet flavor as a result of the increased content of glucose.