A combined convective and radiative heat transfer problem in thermally developing Poiseuille flow in a cylindrical tube is analyzed. A complex form of the nonlinear integrodifferential radiative transfer equation is solved by the discrete ordinates method in an axisymmetric geometry. To check its accuracy, the solution obtained by the discrete ordinates method is compared with that solved by the integral method. A parametric study is also performed for the conduction-to-radiation parameter, optical thickness, wall emissivity, scattering albedo, and linear anisotropic scattering coefficient. The results show a significant effect of the radiation on the thermal characteristics.