In rats, effects of starvation and subsequent refeeding on hepatic polyamine-synthesizing enzymes (ornithine decarboxylase, S-adenosyl-methionine decarboxylase) and on polyamine contents (putrescine, spermidine, spermine), were examined. Following 12 hours of starvation, ornithine decarboxylase activity was reduced markedly (to 13% of controls) and was decreased to levels near zero after 3 days of starvation, whereas S-adenosylmethionine decarboxylase activity declined less drastically (to 50% of controls). This fall in enzyme activities was in good accord with putrescine and spermidine contents which were found to be decreased significantly in rat livers under these conditions. On refeeding, within 3 hours ornithine decarboxylase activity increased about 7-fold as compared to controls, whereas the rise in Sadenosylmethionine decarboxylase activity was less pronounced (to 125% of controls). These changes were accompanied by a normalization of the levels of putrescine and spermidine. Interestingly, hepatic spermidine and RNA contents fluctuated concomitantly. DNA and spermine levels, however, remained almost unchanged during starvation and refeeding periods.