Amalgam fillings using alloy with lathe--cut or spherical particles were placed in 38 Class II cavities of dental students. One part of each cavity was left unfinished in order to maximize differences in preparation quality, whereas the rest of the cavity was well finished. The cavities were replicated prior to restoration, after carving, polishing, and then after one year and four years. Quality evaluation was performed clinically using a scoring system for marginal integrity and by scanning electron microscopy of replicas. After four years the restorations filled with lathe-cut amalgam showed better quality than those made with spherical amalgam. No difference could be detected due to variations in the finishing technique of the margins.