A patient with progressive neurological disease resembling Wilson's disease but in whom Kayser-Fleischer rings were absent, was given 67Cu and 64Cu, orally and intravenously, to measure the rate of absorption of copper using a convolution integral. The data show an abnormal distribution of body copper resulting in low copper concentrations in plasma, urine and liver but with an accumulation in the lower bowel probably due to a defect in mucosal transport. The importance of differentiating this condition from Wilson's disease is stressed.