The role of avian adenovirus isolate PARC-1 as an immunosuppressive agent was investigated using a Newcastle disease virus (NDV) vaccine immune response procedure. The immunosuppressive effect on the humoral immune response was investigated up to 21 days after inoculation with adenovirus. Infected chickens showed a serologic response to NDV that was reduced compared with that of the controls. To further investigate the effect of the virus on major lymphoid organs, the pattern of virus dissemination in various organs was studied at various time intervals after inoculation. Spleen, thymus, bursa of Fabricius, and cecal tonsils of broilers were examined using a dot-immunobinding assay. The virus was found to have a predilection for lymphoid organs, and virus from lymphoid organs was capable of producing disease when inoculated into healthy chickens. The relationship of virus predilection to its immunosuppressive effect also was studied.