Purpose:This in vitro study is to evaluate the microleakage of the universal and self-etch adhesives in selective-etch and self-etch techniques by evaluating dye penetration. Materials and methods: In this study, a total of 48 restoration and caries-free maxillar or mandibular anterior teeth were used. Standardized class V cavities (1.5 mm deep, not beveled, rounded corners) were prepared on buccal surfaces of all teeth, which were gingival edges above from the enamel-cement junction. A total of 48 teeth were randomly separated into four groups. The first group was restored with Clearfil S3 Bond Plus (Kuraray, Tokyo, Japan) in the self-etch technique. The second group was restored with single bond universal (SBU) adhesive L-pop (3M ESPE, St. Paul, USA) in the self-etch technique. The third group was restored with Clearfil S3 Bond Plus (Kuraray, Tokyo, Japan) in the selective-etch technique. The fourth group was restored with single bond universal adhesive L-pop (3M ESPE, St. Paul, USA) in the selective-etch technique. Final finishing and polishing of the restorations were performed by using discs (ZenitFlex, Munich, Germany). They were thermocycled for 5,000 thermal cycles between water baths at 5°C and 55°C. All surfaces were isolated with two layers of nail polish, except up to 1 mm from the restoration margin for correct evaluation of the microleakage. The apices of all teeth were covered with a composite resin (Clearfil Majesty Esthetic, Kuraray, Tokyo, Japan). The teeth were stored in an oven with 2% methylene blue solution for 24 hours. The samples were embedded in acrylic resin in plastic molds. Results: Microleakage scores (count and percentages) for all four groups are shown in Table 2. The Kruskal-Wallis test was applied to determine the differences between microleakage scores in the four study groups at a 0.05 level of significance. No statistically significant difference was found (p > 0.05). Conclusion:The two adhesive systems showed clinically acceptable microleakage values in two different application techniques.