The laser induced T-1(n pi*)<--S-0 phosphorescence excitation spectrum of jet-cooled acetaldehyde has been observed for the first time with a rotating slit nozzle excitation system. The vibronic origins were fitted to a set of levels that were obtained from a Hamiltonian that employed flexible torsion-wagging large amplitude coordinates. The potential surface extracted from the fitting procedure yielded barriers to torsion and inversion of 609.68 and 869.02 cm(-1), respectively. Minima in the potential-hypersurface at theta=61.7 degrees and alpha=42.2 degrees defined the equilibrium positions for the torsion and wagging coordinates. A comparison to the corresponding S-1-state parameters showed that the torsion barrier (in cm(-1)) does not greatly change, S-1/T-1 = 710.8/609.7, whereas the barrier height for the wagging-inversion barrier increases dramatically, 574.4/869.0.