The flow and thermal fields in forced convection over a heated cylinder for both incompressible and compressible flows are studied nondimensionally and numerically. The governing system includes fully two-dimensional Navier^Stokes momentum, energy, and continuity equations in body-fitted coordinates. The effect of Reynolds number (Re) is investigated. In the incompressible case, Re is a function of free-stream velocity. The predicted results are in good agreement with those obtained by the other numerical methods and experimental measurements. In the compressible case, Re is governed by cylinder surface temperature. The characteristics of fluid flow and heat transfer when surface temperature is increased are found to be simitar to those obtained by decreasing incoming flow velocity in the incompressible case.