The purpose of this work is to explore the effect of the presence of two different primary phases on the microstructure and solidification kinetics of Pb-Sn alloys. The experimental results have been compared with predictions obtained from the Newton Thermal Analysis of cooling curves generated by a conventional heat transfer-solidification kinetics model. Three Pb-Sn alloys have been considered in this work in order to explore the solidification characteristics of the eutectic in hypoeutectic, hypereutectic and eutectic compositions. Experimental results indicate that the Pb-Sn eutectic morphology and the solidification rate depend on the nature of the pre-existent primary phase during eutectic solidification. From the observed discrepancies between experimental and simulated results it is concluded that further improvements are needed to simulate the solidification kinetics of eutectic microconstituents in the presence of pre-existing primary phases.