Optimization of photoresist performance in the sub-micron domain is greatly facilitated by the availability of accurate simulation algorithms for the calculation of developed resist profiles. In this paper, a new procedure for the calculation of resist profiles is described. A numerically efficient version of the WKB approximation is implemented for the determination of standing wave intensity and PAC concentration in a model resist film on both silicon and aluminum substrates. Utilizing these PAC concentration profiles, the recently proposed dissolution algorithm based on the least action principle for solvent penetration through the exposed resist film is employed to calculate developed resist profiles.