Several indices of calcium metabolism have been studied in 39 subjects living with a permanent ileostomy after proctocolectomy for ulcerative colitis, and in a control group of 39 healthy volunteers, matched for age and sex. No significant differences were found in plasma levels of calcium, phosphate, magnesium, parathyroid hormone, calcitonin and 25-hydroxy-vitamin D nor in the urinary excretion of calcium and phosphate, but the alkaline phosphatase was raised in the ileostomists. The bone density of the ileostomists was rather low, but the difference from the control subjects was not statistically significant. The absorption of calcium was measured by means of a total body counter. The ileostomists retained significantly more calcium than expected. It is suggested that this may represent the correction of a state of calcium deficiency at the time of proctocolectomy, due to the effects of the colitis and its medical treatment with corticosteroids.