Species differences in the oral pharmacokinetics and absolute bioavailability ($F_{abs}$) of carbamazepine polymorphs (form I and form III) and dihydrate were studied. The pharmacokinetics of each form was investigated in rats following a single oral/intravenous administration of 10 mg/kg and an oral dose of 80 mg/kg, which were compared with the published data obtained from dogs and humans. No significant differences were found in their $C_{max}$, $T_{max}$, $AUC_{0-{infty}}$ and $F_{abs}$ among the forms at the low dose. However, significant differences were observed at the high dose. The $F_{abs}$ of each form was markedly reduced with increasing of doses in species (e.g. $F_{abs}$ in rats ranged from > 82% to 38.4% - 56.0%). At a comparable dose, the $C_{max}$, and $AUC_{0-{infty}}$ of rats and humans were about 3-10 times higher than in dogs. The absorption rate of form III in rats exhibited a similar trend to that in humans, and was far higher in dogs. A multi-peak phenomenon in plasma curves was observed in rats and humans, but not in dogs. In conclusion, rats appear to be a better predictor of carbamazepine polymorphs absorbed in humans, and form III may be more suitable as a pharmaceutical crystal.