  We report on the determination of the deconfining temperature in SU(3) pure
gauge theory, using the Symanzik tree level improved action, on lattices of
size 3 x 12^3, 4 x 16^3, 5 x 20^3, 6 x24^3. We find that the asymptotic scaling
violation pattern is similar to the one observed using the Wilson action. We
conclude that the irrelevant operators do not affect, in the range of couplings
considered, the lattice beta function. An analysis based on an effective
coupling formulation shows an apparent improvement.
