Objectives: Evaluation of postoperative sensitivity in posterior teeth restored with etchand- rinse adhesive and composite resin after application of 2% chlorhexidine solution. Method and Materials: Thirty participants with similar dental caries on both sides of the jaws were selected. After cavity preparation, each tooth was randomized to one of the following restoration methods. Teeth in the control group were restored using etch-and-rinse resin adhesive (Single Bond, 3M ESPE) and universal microhybrid composite resin (Filtek Z250, 3M ESPE). Restoration of teeth in the experimental group was similar to the control group except that 2% chlorhexidine solution (Concepsis, Ultradent) was applied on the etched dentin for 60 seconds. Subjects were recalled for evaluation of postoperative sensitivity at 1 day, 1 week, 1 month, and 6 months. Data were analyzed by Fisher exact test (α = .05). Results: The experimental group showed significantly less postoperative sensitivity (8 teeth) compared with the control group (20 teeth) at the 1-day recall (P .05; Fisher exact test). Conventional restorations were comparable to teeth treated with chlorhexidine at other recall times (P > .05). Conclusion: Chlorhexidine significantly decreased immediate postoperative sensitivity of posterior teeth restored by composite resin. Schlagwörter: chlorhexidine, dentin conditioning, posterior composite resin restoration, postoperative sensitivity, randomized clinical trial