To overcome some of the disadvantages of present cyclosporin A (CsA) therapy, lipid microspheres incorporating CsA (lipo-CsA) were designed and their selective transfer to thoracic lymphatic systems was evaluated in vivo. It was found that concentrations of CsA in lymph-ducts were about 46 times higher after 2 h and 9-10 times higher after 3 h following oral administration of lipo-CsA, compared with those of conventional CsA. The concentrations in plasma produced by lipo-CsA were also higher than those produced by conventional CsA.