Cadmium (Cd) is a component in quantum dot 705 (QD705). Whether QD705 behaves similar to Cd in vivo is of great concern. We compared the distributional kinetics of cadmium chloride (CdCl(2)) and QD705 in mice after intravenous injection. QD705 showed a longer plasma and body retention than CdCl(2) and could be detected in the brain during early exposure. While both the liver and spleen demonstrated a constant Cd concentration for 28 days after QD705 injection, it is likely that this represents intact QD705 stored in mononuclear phagocytes. The kidneys showed a time-dependent accumulation of Cd in the QD705-exposed animals. By day 28, Cd in the kidneys from QD705 was 3-fold that of CdCl(2). QD705 and CdCl(2) have very different kinetics in distribution and metabolism. The long body retention of QD705 in the kidneys may mean that QD705 has even more renal toxicity than CdCl(2).