In several instances, high-level quantum chemical computations have provided information critical to the correct interpretation of experimental observations. Accurate theoretical values of the acetylene singlet-triplet gap have shown that the most straightforward interpretation of several experiments by Lisy and Klemperer, Field and co-workers, and Suits and co-workers, is not actually the correct one. In addition, these experiments and others by researchers such as Wittig and co-workers have driven progressively more refined computational work. Thus, the history of research into the excited states of acetylene exemplifies the potential for synergy between theory and experiment in chemical physics.