Objective: To determine and compare the microleakage of a conventional acid-etched, light-cured lingual retainer adhesive system with a recently developed antibacterial monomer-containing adhesive with and without etching. Methods: Sixty human mandibular incisors were separated into three groups of 20 teeth each, which received the following treatments: group 1 (control) = Transbond LR (3M Unitek), conventional lingual retainer bonding; group 2 = Clearfil Protect Bond (Kuraray Medical) with acid-etching; and group 3 = Clearfil Protect Bond without acid-etching. The wire in each was 0.0215-inch multistranded PentaOne (Masel Orthodontics). Samples were sealed with nail varnish, stained with 0.5% basic fuchsin, and sectioned. Transverse sections were evaluated under a stereomicroscope and scored for microleakage in millimeters at the composite-enamel interface. Statistical analysis was performed by Kruskal-Wallis and Mann-Whitney tests with Bonferroni correction. Results: Group 2 had less microleakage (0.11 ± 0.19 mm) than group 1 (0.26 ± 0.30 mm) or group 3 (0.24 ± 0.27 mm). However, the difference in the microleakage of the composite-enamel interface among all investigated groups was not significant (P > .05). Conclusion: The findings of this study do not speak against using an antibacterial monomer-containing self-etching adhesive to bond lingual retainers. World J Orthod 2009;10:196–201.