Numerical results for laminar gas flow in annuli, with fluid properties varying due to their temperature dependence, have been obtained for both fully developed and uniform entry velocity profiles by solving the coupled boundary layer equations in finite difference form. All annuli computations were made with a radius ratio of 0.25, which differs sufficiently from the limiting cases of circular tubes and parallel plates to portray annular geometry well. In addition to variable property results, predictions were obtained for three of four fundamental, constant property solutions with uniform entering velocity profiles. The fourth solution is available in the literature but the approximate velocity distribution is in error in the entrance region, so a new hydrodynamic solution is presented as well.