The dissolution of second phase particles in a 319-type (Al-Si-Cu-Mg) casting alloy during heat treatment has been characterized by image analysis and microprobe testing of metallographic specimens.  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 temperatures between 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 quantified by 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.