On the perturbation expansion of the KPZ equation

We present a simple argument to show that the p-function of the cl-dimensio nal KPZ equation (d greater than or equal to 2) is to all orders in perturb ation theory given by beta(g(R)) = (d-2) g(R)- [2/(8 pi)(d/2)] Gamma(2 - d/2) g(R)(2) Neither the dynamical exponent z nor the roughness exponent zeta have any c orrection in any order of perturbation theory. This shows that standard per turbation theory cannot attain the strong-coupling regime and in addition b reaks down at d=4. We also calculate a class of correlation functions exact ly.