Consideration is given to the absorption of radiant energy on nonblack, concave cylindrical surfaces on which radiation from some external source is incident. The multiple reflections which may occur between various parts of the concave surface are fully accounted for. The analysis is carried out both for diffusely, and for specularly, reflecting surfaces. Also included are both situations where the surface is fully illuminated (though not necessarily uniformly) or where a portion of the surface lies in a shadow. For a wide range of surface configurations, numerical results are presented for the surface distribution of the absorbed energy and for the total energy absorbed.