Abstract: This invention is based upon the application of amniotic cells--in particular, viable epithelial cells--to clinical procedures including the treatment of diseased or damaged tissues, e.g. in joints denuded of cartilage and vascular grafts. The invention also provides prosthetic devices which incorporate amniotic cells, and compositions for cosmetic use based upon amniotic cells or cell extracts. A further development uses amniotic cells in the form of a semi-permeable membrane, or coated onto, for example, microspheres; these structures act as filtration devices for the removal of toxic materials from, for example, blood or urine.