Simple Calculation of Instanton Corrections in Massive N=2 SU(3) SYM

We give an explicit derivation of the Picard-Fuchs equations for N=2 supersymmetric SU(3) Yang-Mills theory with $N_f<6$ massive hypermultiplets in the fundamental representation. We determine the instanton corrections to the prepotential in the weak coupling region using the relation between $\tr<\phi^2>$ and the prepotential. This method can be generalized to other gauge groups.