Eugenol is known to have a detrimental effect on both composite resin and dentin bonding agents. The purpose of this in vitro investigation was to compare the microleakage among groups of resin-luted inlays when the cavity preparations were pretreated with a eugenol-containing temporary cement, a eugenol-free temporary cement, or no temporary cement. Class 5 inlay preparations (20 per group) were completed in extracted human molars. Following the fabrication of composite resin inlays, the preparations were filled with either a eugenol-based temporary cement, a eugenol-free temporary cement, or no cement. After removal of the cement from the cavity preparations and application of a dentin bonding agent, the composite inlays were luted with a resin cement, thermocycled, stained, sectioned, and evaluated for microleakage under a stereomicroscope. None of the groups exhibited significant leakage at the enamel margins. Both of the groups treated with temporary cement leaked at the nonenamel margins significantly more than the control (no cement) group. No significant difference in leakage was demonstrated between the groups treated with the eugenol-containing and the eugenol-free temporary cements.