This paper will describe a methodology for developing next generation web-based medical systems. Recent web-based technologies have created completely new possibilities to various medical information systems. Nevertheless, transferring 3D patient models through usual low band-width networks is difficult because of their large data size. We address this problem by making use of Lattice, an extension for X3D proposed at the Web3D Consortium, which represents high quality surface shape with small data size. Taking advantage of Lattice, detailed anatomical 3D models are rapidly transferred within a few seconds through low band-width networks. Anatomical Lattice models are semi-automatically generated from CT/MRI data. Our system also provide a multi-user functions which can be used as remote clinical conferences or instructing surgical procedures. Some practical applications of our system are also presented.