Abstract: Researchers have developed an Enzyme-Linked Immunosorbent Assay (V-ELISA) to detect antibody against the C-terminal region of the Newcastle disease virus non-structural protein V. Another ELISA to detect antibody against a C-terminal polypeptide of structural P protein (P-ELISA) was also developed. Antibody responses to V and P proteins in chicken sera immunized with recombinant proteins were detected by using V-ELISA and P-ELISA with the minimum cross reactions. And using V-ELISA and P-ELISA, antibodies to V and P were also detected in yolk of eggs from chickens immunized with live NDV vaccine. These results indicate that the internal NDV proteins can be used as diagnostic antigens for detection of NDV infection.