Sucrose-14C was administered to rats in solutions of 12.5 and 50%. Radioactivity was found in renal cortical cells and was partly sedimentable on centrifugation of homogenates. Over a 24-hour period, there was a sharp decrease in the amount of non-sedimentable radioactivity whereas no net change in sedimentable radioactivity occurred during this period. Utilizing isopycnic density gradient centrifugation, it was found that part of the sedimentable radioactivity distributed with lysosomal acid phosphatase. These findings, in conjunction with histochemical data of others, suggest that sucrose-induced vacuolization of renal cortical cells is a reflection of the incorporation of sucrose into phagolysosomes. Since this process is most likely mediated through pinocytosis and not by osmotic changes, the term ‘osmotic nephrosis’ appears to be inappropriate when applied to describe the etiology of sucrose nephrosis.