A method for implanting cells is disclosed which employs a chamber having a wall forming porous boundary between the host and implanted cells. According to the method, a given number of cells (N) is placed within the porous boundary of a given area (A) such that the quantity A/N is less than about 200 mum2/cell. The porous boundary has a pore size, an ultimate strength, and a metabolic transit value that assures the survival of the cells during the critical ischemic period and afterward.