Four porous synthetics were tested for their applicability as cartilage replacement in the reconstruction of the auricle: teflon velour, filamentous dacron, porous polyethylene and proplast II. After formation of a fold, the implants were sutured into subcutaneous cavities of the abdominal skin of rats or fixed with fibrin adhesive. Histological and scanning-electron-microscopic examinations have so far been performed after 1 and 3 months. Form stability with persistence of the desired skin fold was good when the material was not too thin or too thick. The infection rate was surprisingly low; skin necroses occurred largely in the area of transfixion sutures. The porosity appears to promote adaptation of the skin to the material and to thus counteract an effacement of the skin fold. The best form stability was evidenced by thermoplastic polyethylene, which was thus also chosen for first clinical applications.