It has not been fully elucidated how endocrine-disrupting chemicals disrupt hormone functions or how strong their effects are compared with natural hormones. There is little information concerning the effects of tributyltin (TBT), one of the endocrine disrupters on living organisms. Although TBT at high concentration induced apoptosis in PC12 cells, TBT at low concentration inhibited the DNA fragmentation in the cells cultured in serum-free medium or in medium containing 6-hydroxydopamine. The cell viability grown in both medium conditions increased after treatment with TBT. These findings suggest that TBT exerted a apoptosis-inducing and -inhibiting effect. These diverse effect of TBT on apoptosis would cause serious damages on cell differentiation.