The dissolution of second phase particles in a 319-type (Al-Si- Cu-Mg) aluminum casting alloy has been quantified by image analysis of metallographic specimens as well as an electron microprobe technique. The initial phase content of the as-cast material, and the change in volume fraction of each phase following solution treatment for various times at 480°C and 505°C, was determined by analysis of particles observed by backscattered electron microscopy. Furthermore, the change in dendritic alloy content during solution treatment was measured using electron microprobe analysis in order to estimate the relative volume fraction of second phase particles dissolved. Finally, a non-isothermal dissolution model was used to predict the dissolution behaviour during solution treatment and comparisons are made between the model predictions and experimental measurements.