Purpose: The purpose of this study was to evaluate the sealing ability of a three different restorative materials used in restoring root caries lesions.Materials & methods: A total of 60 extracted human upper premolar teeth were divided into 3 main groups according to restorative material used. Group 1 restored with resin composite with self etch adhesive, group 2 restored with resin modified glass ionomer, group 3 restored with self adhesive flowable composite. Each group were further subdivided into 2 groups according to load cycling, group with load cycling and other group without load cycling.Class V cavities were prepared in the roots, so that the cavities were completely in cementum just below cemento-enamel junction on the buccal surfaces of premolars using a high speed hand piece then restored with each restorative material according to the manufacturers’ instructions. All restorations finished and polished. 10 teeth of each group were individually & vertically mounted in the lower fixed compartment of a computer controlled materials testing machine (Model LRX-plus; Lloyd Instruments Ltd, Fareham, UK) loadcell of 5 kN. Each sample underwent 5000 cycles at loads of 60N. After that, apex of all teeth sealed with Zn(Po)4 and wax then, all surfaces, except for the restorations and 1 mm from the margins were coated with two layers of nail varnish, and covered with aluminium foil. All of the teeth were immersed in a 2% methylene blue dye solution for 24 hours. The teeth were then rinsed under tap water and dried. They were sectioned faciolingually using diamond disc. Sections were assessed for dye penetration with a stereo-microscope (Japan) at 50x magnification. Dye penetration at the restoration/tooth interface was scored from 0 to 3.The data were collected, recorded and tabulated. Two-way analysis of variance ANOVA test of significance comparing variables affecting leakage score mean values. Two samples of each group were tested under scanning electron microscope to observe adaptation of restoration to tooth at the interface.Results: Results of the present study showed that the restorative materials significantly affected microleakage scores. While it showed that application of load cycling had no significant effect on microleakage scores. Conclusions: Within the limitations of this study, it could be concluded that: All tested restorative materials suffered microleakage. Easy one self-etch adhesive restorative group showed the highest microleakage scores followed by Fuji II Light- Cure restorative group while Fusio Liquid Dentin restorative group showed the lowest microleakage scores. Load cycling had no significant effect on microleakage. Scanning electron microscopic examination was indicative