This study evaluated the microleakage of a flowable polyacid-modified resin composite used as a fissure sealant on air-abraded teeth in comparison to a resin-based fluoride sealant. Sixty extracted human third molars were divided into six subgroups (n=10) under two main groups (fissure sealant materials). The occlusal surfaces of the teeth were air-abraded at 80 psi using 50 pun particles of aluminum oxide for 30 seconds, followed by rinsing and drying. Delton FS+ (Dentsply International) and Dyract Flow (Dentsply DeTrey) were applied to the teeth in subgroups following application of: a) an acid etching and bonding agent, b) bonding agent alone or c) air-abrasion alone, respectively. Acid etching (Delton EZ Etch, Dentsply International) and bonding agent application (Prime & Bond NT, Dentsply DeTrey) were done according to the manufacturers' instructions. The teeth were thermocycled for 500 cycles between 5degreesC and 55degreesC with dwell time of 15 seconds. Basic:fuchsin (0.5%) staining followed: by buccolingual sectioning was performed. Microleakage was evaluated at 20x optical magnification. Kruskal-Wallis test was used to make comparisons among six subgroups. Pairwise comparisons were done with the Mann-Whitney U test with the level of significance set as alpha=0.05.