The purpose of the present study was evaluate the biological compatibility of materials used to manufacture prosthetic appliances. A heat-polymerized colorless resin and one visible light-cured denture base material were tested by the implantation of probe discs, in the dorsal connective tissue of 12 Wistar rats. The animals were sacrificed at 7, 14, 21 and 28 days after implantation. The specimens were prepared for light microscopy observation. It was noted that either after light microscopy observations, both resins demonstrated a good level of biocompatibility within the connective tissue of the dorsum of the animals studied.