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Air-assist fuel sprays have been investigated experimentally with exciplex laser-induced fluorescence visualization and computationally with the KIVA-3 code. The exciplex-fluorescence technique provided simultaneous but distinct cross-sectional images of the liquid and vapor fuel distributions under simulated light-load conditions in both an atmospheric-pressure test rig and in a motored two-stroke engine. The computations resolved the flow through the injector passages upstream of and around the poppet, and included the effects of aerodynamic drop breakup, drop collisions and vaporization. Both the measurements and the calculations show that the fuel initially emerges from the injector as a hollow-cone jet. This two-phase jet collapses downstream as entrainment of air produces a low-pressure region beneath the poppet.