Hartunian's theory for the curvature of a shock wave progressing into quiescent gas near a wall is extended to the cases of two parallel walls, of a rectangular tube and of a circular tube. Shock curvature is considered as caused both by laminar and by turbulent boundary layers along the walls behind the shock. For a completely laminar boundary layer, the axial extent of the curved shock in the cases of two parallel walls and of a circular tube is found to be 0.760 and 0.783, respectively, of Hartunian's single wall result. The correction arising from the finite length of the boundary layer is calculated. This correction is found to be negligible provided the boundary layer length is larger than approximately one-half the distance between the walls. An estimate is presented for the correction arising from the flow behind the foot of the shock. This correction is of some importance at very low initial pressures. An approximate method is given to find the curvature of shock fronts which are followed by a relaxation region. The results obtained are in good agreement with the available experimental data.