Orphan receptor TR3/nur77, a member of nuclear receptor superfamily, is a product of immediate-early gene which is expressed rapidly after induced by several proliferation factors such as EGF, FGF, NGF, PDGF or phorbol ester, and different apoptosis inducers. It is similar in structure with the members of steroid/retinoid receptor superfamily that all have a DNA-binding region of two zinc-finger and a ligand-binding region. As a transcription factor its complex functions are involved in proliferation, differentiation and apoptosis of cells. Recently there is an important development about the TR3 receptor in the mechanism of inducing apoptosis. After treated by different apoptosis inducers TR3 expressed increasingly, and it is found surprisingly that TR3 translocates from the nucleus to mitochondria to induce cytochrome c release and apoptosis. That is, mitochondria targeting of TR3 but not its DNA binding and transactivation is essential for its proapoptotic effect. This is a new model may be a very significant pathway in the regulation of cell signal transduction especially in the apoptosis.