The surfaces of a fin from which heat is rejected solely by radiation may have to be coated to obtain high values of thermal emissivity. In order to determine the influence of the conductive resistance of a coating on the thermal performance of a fin, an analysis was undertaken. Two equations are derived to describe the heat-transfer characteristics of a coated fin: One, a differential equation for the temperature profile on the radiating surfaces of the coating; and two, an equation for the relative thermal performance of the fin in terms of fin efficiency. The equations are solved numerically, and the fin efficiencies are plotted as a function of two dimensionless parameters which appear in the differential equation. These efficiencies are compared with those for fins in which the conductive resistance of the coating is ignored.