We have investigated the interference effects in the two-color dissociation of IBr using fundamental (560 mn) and its second-harmonic (280 mn) light. We have performed one-dimensional photofragment translational spectroscopy in the presence of two-color excitation. In the strong-excitation regime for the fundamental light (similar to1.3 x 10(10) W cm(-2)), the yield of the spin-orbit excited iodine atoms dissociated from IBr molecules shows an oscillating behavior that is dependent on the relative phase between the fundamental and the second-harmonic light. This phase-dependent behavior can be explained by the interference between a one-photon transition induced by the second-harmonic light and a dipole-forbidden two-photon transition induced. by the strong fundamental light. (C) 2002 Elsevier Science B.V. All rights reserved.