Objective: The purpose of this investigation was to evaluate microleakage in Class II cavities restored with the condensable resin composite SureFil, placed with or without a liner and 1 of 2 different dentin bonding agents. Method and materials: Extracted noncarious human teeth were randomly divided into 4 groups of 15 each and restored according to manufacturer's instructions: group 1, SureFil and Prime & Bond NT; group 2, SureFil and PQ1; group 3, SureFil, PermaFlow, and PQ1; group 4, Heliomolar and Syntac Single-Component (control). Specimens were stored in 37°C water for 24 hours. All specimens were thermocycled between 5°C and 55°C for 500 cycles. Each specimen was immersed in 0.2% basic fuchsin dye for 24 hours and then sectioned longitudinally and horizontally. Dye penetration at enamel and cementum margins were viewed at 330 magnification by 2 independent, calibrated evaluators. Specimens exhibiting dye penetration = 0.1 mm beyond the cavosurface margin were considered to have leakage. Results: Chi-square tests revealed no statistically significant differences in the presence of microleakage when all groups were analyzed together. However, 2 by 2 comparisons revealed that group 3 had significantly fewer specimens with microleakage than did groups 1, 2, or 4. Conclusion: To limit microleakage, a flowable composite should be used as a liner when a condensable composite material is used.