A survey was done on 39 nephrectomized patients who underwent our routine radionuclide kidney study including blood flow imaging at various periods postoperation. Perfusion of varying degree was demonstrated in the area of the nephrectomized kidney in 17 patients showing equal or less activity than the actual kidney. This so-called phantom kidney was reproducible in the same patient and was found four weeks to ten years after nephrectomy. Thirteen phantom kidneys were found on the left side and four on the right. Seven were after simple nephrectomy, four after radical nephrectomy, and six after nephroureterectomy. Besides being a source of error in interpretation in kidney imaging, the appearance of this residual postnephrectomy blood flow is difficult to explain, particularly in the cases of radical nephrectomy.