A method is presented for predicting the characteristics of practical nonisothermal-fin arrays from the results of the previous reports on isothermal ones. According to this method, the effects of the fin-geometry, thermal conductivity, and temperatures on the heat-transfer characteristics have been quantitatively clarified. A heat-transfer experiment on a fin array with the fin efficiency of about 80% and the hemispherical emissivity of 0.67 has verified the validity of the present method of prediction.