We have isolated and characterized the chicken junD gene. It does not contain an intron; its upstream regulatory sequences lack the AP-1-binding site seen in c-jun but include two CRE elements. Downstream untranslated sequences do not show the destabilizing signal ATTTA. The amino acid sequence of the chicken JunD protein is closely related to that of mouse JunD in the dimerization and DNA contact surfaces of the carboxy-terminal region; additional homologies to mouse JunD are seen in acidic and amphipathic amino-terminal domains. Chicken JunD contains stretches of oligoglycines, alanines and prolines, possibly acting as hinges that connect functionally distinct domains of the protein. Chicken junD is broadly expressed at low basal levels in differentiated tissues and at somewhat higher levels in cultured fibroblasts. The cDNA clone of junD was transcribed and translated in vitro. The resulting JunD protein migrates in between 40 and 50 kDa in an SDS gel and can be precipitated with an antibody prepared against a polypeptide consisting of the carboxy-terminal 100 amino acids of mouse c-Jun.