This paper presents the effect of variable area ducts and axial temperature gradients on the nonlinear distortion of a traveling wave. Quasi-onedimensional continuity, momentum and energy equations for isentropic flow are solved using a wave front expansion technique. An evolution equation for the slope of the wave front is obtained. This nonlinear ordinary differential equation can be integrated to obtain a solution in closed form for the slope of wave front. The solution may admit singularity for the compression wave fronts. The analysis considers pure compression and pure expansion traveling waves. A general criterion is developed for the steepening of a compression wave front into shock. A general formula is obtained for the location of shock formation. The effects of area variation, axial temperature gradient, and their combined effect on the nonlinear distortion of traveling wave are studied. A number of examples highlighting these effects are presented in the paper. © 2003 by M. Tyagi and R. I. Sujith.