The absorption of calcium, magnesium, and zinc was studied by the metabolic balance technique at two fat intake levels in nine patients with fat malabsorption. The net absorption of all three minerals was significantly higher from the 40-g fat diet than from the 100-g fat diet. The data indicate that the lower fat content was the main reason for the increased mineral absorption, although the low-fat diet contained larger amounts of the minerals studied than did the high-fat diet.