The present invention is directed to novel apoptosis polypeptides such as the Apop1, and Apop3 proteins and related molecules which are involved in modulating apoptosis and to nucleic acid molecules encoding those polypeptides. Also provided here are vectors and host cells comprising those nucleic acid sequences, chimeric polypeptide molecules comprising the polypeptides of the present invention fused to heterologous polypeptide sequences, antibodies which bind to the polypeptides of the present invention and to methods for producing the polypeptides of the present invention. Further provided by the present invention are methods for identifying novel compositions which modulate the biological activity of Apop1, Apop2, and Apop3, and the use of such compositions in diagnosis and treatment of disease.