Studies in uremic rats were performed to see whether or not the long-term administration of therapeutical doses of 1,25-Dihydroxyvitamin D<sub>3</sub> or 1α-hydroxyvitamin D<sub>3</sub> would induce histological changes in the aorta or increase the calcium content of the aorta or the heart. In contrast to observations of others, no effect of both vitamin D sterols could be observed on both investigated tissues. However, the remnant kidneys of the rats treated with both vitamin D compounds showed a significantly increased calcium content. According to these results one cannot exclude that the chronic application of active vitamin D metabolites has induced a calcium deposition in the remnant kidney. This finding deserves special attention, although we found, on the other hand, no evidence that an underlying arterial disease is aggravated by this therapy.