It has previously been reported that in rat liver the rates of synthesis and degradation of ferritin labelled with [14C]leucine or arginine are dependent on the iron status of the rats. It has also been concluded that isoferritins differ markedly in their rates of turnover. Here we provide experimental evidence which shows that the rate of degradation of rat liver ferritin (labelled by injection of [14C]bicarbonate to minimise problems of reutilisation) is unaltered by repeated iron injection, although ferritin synthesis is stimulated. Our data also strongly suggest that the proposed differential degradation of isoferritins is improbable.