Patients admitted for major vascular reconstruction operations received an i.v. dose of 65Zn. From the increased whole-body retention of 65Zn and the findings on other parameters it was concluded that the post-operative zinc metabolism of these patients differed from that of the control subjects. Unexpectedly, this difference persisted for several months. These patients can probably serve as controls in studies of patients who have undergone surgery of the intestinal tract. Increase of whole-body retention of 65Zn may be a sensitive indicator for subclinical zinc deficiency, but application in practice is hampered by the long duration of the period required for the measurement. From the present results it seems likely that measurement of the retention of 65Zn in the forearm as a function of time yields the same information but in a considerably shorter time.