Using recently developed coupled-cluster response methods, accurate potential curves for the X (1)Sigma(g)(+) amd B (1)Sigma(u)(+) electronic states of Ar-2 are evaluated and the lowest rovibronic energy levels are calculated. The results are in very good agreement with the experimentally available spectroscopic data, and suggest a reassignment of the experimental vibrational numbering in the B 1 Sigma(u)(+) state.