Starvation and difluoromethylornithine (DFMO) administration have profound affects on intestinal proliferation, ornithine decarboxylase activity, and tissue polyamine levels. Diamine oxidase activity may play a role in the regulation of proliferation, and the activity of this enzyme may be influenced by ornithine decarboxylase activity. To determine if diamine oxidase is influenced by starvation and DFM administration, ileal diamine oxidase activities were determined on mucosal homogenates from five groups of rats: fed control, starved for 48 h, fed group receiving DFMO, a starved/refed group, and a starved/refed group receiving DFMO. The homogenates from starved rats were found to have decreased ornithine decarboxylase activity and increased diamine oxidase activity when compared to control values. The homogenates from the DFMO group also were found to have decreased ODC activity however, mucosal diamine oxidase activity was also decreased. Refeeding produced a dramatic increase in ornithine decarboxylase activity and a minimal change in diamine oxidase activity. The preservation of diamine oxidase activity during starvation implies a need for the enzyme not related to mucosal proliferation or digestion. However, in the fed state, diamine oxidase activity may be more dependent on ornithine decarboxylase activity or its reaction product putrescine.