The field of cell encapsulation is advancing rapidly. This cell-based technology permits the local and long-term delivery ofa desired therapeutic product reducing or even avoiding the need ofimmunosuppressant drugs. The choice of a suitable material preserving the viability and functionality of enclosed cells becomes fundamental if a therapeutic aim is intended. Alginate, which is by far the most frequently used biomaterial in the field of cell microencapsulation, has been demonstrated to be probably the best polymer for this purpose due to its biocompatibility, easy manipulation, gel forming capacity and in vivo performance.