The importance of the induction of ornithine decarboxylase to the development of GGTase foci is examined in the classic initiation-promotion assay. This was accomplished by examining the complete foci system in the presence and absence of alpha-DFMO, an irreversible inhibitor of ornithine decarboxylase, at concentrations capable of inhibiting both phenobarbital stimulated and control levels of the enzyme. Although the hepatic enzyme was inhibited by the alpha-DFMO, there was no decrease in the progression of formation of the GGTase foci.