Cadmium (Cd) is a toxic metal that can cause renal proximal tubular cell damage. Our previous research demonstrated that Cd induces apoptosis by suppressing the BIRC3 gene expression in human proximal tubular cells (HK-2 cells). BIRC3, a member of BIRC family, inhibits apoptosis by suppressing caspase activity. Cd has been shown to induce caspase-3 activation through the suppression of BIRC3 expression in HK-2 cells. In this study, we examined Birc family gene expression in the kidney and liver of mice exposed to Cd for 67 weeks. Cd exposure decreased the expression of Birc3 in the kidney but increased Birc3 expression in the liver of mice. In our previous in vitro study, Cd decreased BIRC3 expression predominantly in proximal tubular cells. The present findings strongly indicate that the decrease in BIRC3 gene expression is implicated in the induction of apoptosis by Cd in proximal tubules.