The pancreas ferritins from chickens, ducks, cattle and pigs were isolated by thermal denaturation, ammonium sulphate fractionation and DEAE-52 cellulose anion exchange chromatography separately, in order to obtain the characteristics both subunit types and isoelectric points. Four ferritins such as chicken pancreas ferritin (ChPF), duck pancreas ferritin (DPF), cattle pancreas ferritin (CaPF), and pig pancreas ferritin (PPF) showed different mobility in polyacrylamide gel electrophoresis (PAGE). The relative molecular masses (M(r)) of these ferritin were indicated to be M(r) (ChPF) > M(r) (DPF) > M(r) (CaPF) > M(r) (PPF), which are all bigger than that in horse spleen ferritin (HSF). Sodium dodecyl sulfate (SDS)-PAGE results indicate that ChPF, DPF, CaPF and PPF consist of H and L subunits, showing different ratios of H/L subunits. Two subunit types in the ferritin were further identified by peptide-mass fingerprinting (PMF) technology. The four ferritins such as ChPF, DPF, CaPF and PPF in denatured-isoelectric focusing (IEF) gel show the subunit polymers containing from 3 to 6 with different pI values, respectively. These phenomena reveal the complicated interactions and different polymers between H and L subunits in the ferritins. There are differences both interaction intensities and polymers in the ferritin subunits coming from different mammals. These heterogeneity may response to the rate of iron release in ferritins and to the detoxification requirement of iron in animals in vivo.