Formulation is given for efficient parabolic equation solution of radiowave propagation in inhomogeneous atmosphere and over irregular terrain. Both standard and wide angle parabolic equation derivations are presented. Impedance boundary conditions are used to characterize the ground. A tropospheric boundary condition based on the exact solution of Schroedinger equation in a quarter plane is derived. To permit efficient modeling of the irregular boundary, the parabolic equation together with the boundary conditions is transformed into a numerically generated curvilinear coordinate system. Finally, formulation is presented for a finite difference solution using Crank- Nicolson implicit scheme. Radiowave propagation, Parabolic equation, Finite differences.