To see the cellular localization mechanism of membrane proteins in the hepatocyte in situ, we introduced cDNAs of facilitated-diffusion sugar transporters, GLUT1, GLUT3, GLUT4, and GLUT5, and a Na⁺-dependent active sugar transporter SGLT1 into the rat liver by the in vivo electroporation method and the particle gun method, and the localization of their products was analyzed by immunofluorescence microscopy. SGLT1 was strictly restricted to the bile canalicular (apical) domain, whereas GLUT1 was found in the sinusoidal (basolateral) membrane of hepatocytes. GLUT3 and GLUT5 were present along the whole aspects of the plasma membrane with a tendency for the bile canalicular membrane to be enriched with transporters as compared with the sinusoidal membrane. GLUT4 remained in the intracellular compartments. Simultaneous expression of two of the transporters confirmed these results. Compared with membrane localization of sugar transporters in MDCK cells, GLUT1, GLUT4 and SGLT1 exhibited a similar localization pattern. On the other hand, localization of GLUT3 and GLUT5 was different from that in MDCK cells. These observations suggest that hepatocytes in situ may have a different localization mechanism for sugar transporters from that in MDCK cells. In addition, the in vivo electroporation and the particle gun methods seem to be useful tools for the introduction and analysis of foreign genes in the liver in situ.