The mechanism by which hydrophobic solutes such as oils move from emulsion droplets into surfactant aggregates such as micelles continues to be debated. Controlling roles of micelle adsorption, micelle pinch-off, molecular diffusion or of rapid micelle uptake have been proposed by various research groups. In this study, nearly monodisperse alkane-in-water emulsion droplets were mixed with aqueous micellar solutions, allowing solubilization to proceed. Because these emulsions were nearly monodisperse, we were able for the first time to observe, using static light scattering, the progressive decrease in average droplet size due to solubilization, and to analyze the rate of this decrease using a population balance approach to calculate the mass transfer coefficient. We studied the effect of oil chain length, surfactant type and concentration, and the aqueous phase viscosity on the mass transfer kinetics. The influence of viscosity and of surfactant concentration, in particular, provide insight into the role of molecular diffusive processes relative to interfacial mechanisms. Understanding solubilization mechanisms is important in a host of natural and industrial processes, including nutrient absorption and release of pharmaceutical agents.