Objectives: In this in vitro study, the degree of marginal microleakage at cement was evaluated when two materials were used for the composite resin inlays cementation. Methods: Two standard occlusive-proximal cavities were made on rigid human third molar. After the preparations have received temporary restorations and a eugenol-free temporary cement, ,the inlays were cemented with a dual resin cement or a resin-modified glass ionomer cement. After that, it was performed thermocycling and impermeability, except on the cervical wall, and the immersion in a staining solution. Then, the teeth were seccionated at mesio-distal direction and were observed with a stereoscopic magnifying glamicroscope. Two calibrated examiners had set predetermined values to the microleakage. Results:It was observed that there was a statistically significant difference between materials. Conclusions: The dual resin cement is more resistant to the microleakage than the glass ionomer cement.