Liposomes have been proved to be effective as carriers of water-soluble drugs into the central nervous system, but the mechanisms by which water-soluble drugs encapsulated in liposomes permeate the blood-brain barrier(BBB) are not clear. In order to elucidate the mechanisms, the authors investigated the permeability of liposome encapsulated cisplatin [cis-diamminedichloroplatinum (II), CDDP] across in vitro BBB model compared with that of free CDDP. This in vitro BBB model is consisted of primarily cultured bovine brain microvessel endothelial cell (BMEC) monolayer onto the collagen-coated polycarbonate membrane which is put in side by side diffusion cells. This in vitro BBB model matches in vitro BBB in morphology and enzymatic activity, and has been used in many transport studies. The result showed that liposome encapsulated CDDP permeated across BMEC monolayers and the permeability was significantly attenuated by metabolic inhibitor, 2-deoxyglucose treatment (p<0.05 by Student's t-test). Our findings confirmed that CDDP encapsulated in liposomes could be transported through BBB by way of energy-dependent transcellular pathway.