Objectives: To evaluate the 18-month clinical performance of 4 adhesive strategies in posterior composite restorations inserted by private practice clinicians with advanced clinical degrees in Operative Dentistry. Methods: Upon approval by an Institutional Review Board and patient's informed consent, 161 restorations were inserted in 50 subjects (average age=32.6) to treat caries lesions (24.8%) or to replace existing restorations (75.2%). The adhesives OptiBond FL (3-step etch&rinse), OptiBond SOLO Plus (2-step etch&rinse), OptiBond XTR (2-step self-etch), and OptiBond All-in One (1-step self-etch) were applied as per manufacturer's (Kerr Co.) instructions (40±2 restorations per adhesive). Preparations in molars or pre-molars (26.7% multi-surface restorations, 73.3% one-surface restorations) were restored with a nanofilled composite resin (Filtek Z350XT, 3M ESPE) under local anesthesia and rubber dam isolation. Restorations were evaluated at baseline, 6 months, 1 year, and 18 months using high-resolution digital photographs and the USPHS modified criteria (Cvar & Ryge, 1971): color match, interfacial staining, recurrent caries, occlusal wear, marginal integrity, surface texture, functional occlusion, postoperative sensitivity, axial contour, proximal contact, and retention. Statistical analyses (SPSS 21, IBM SPSS) included the McNemar and the Mann-Whitney non-parametric tests (p<0.05). Results: At 18 months, 148 out of 161 restorations (recall level of 91.9%) were evaluated. The number of alfa ratings (above 95% for all parameters) remained statistically similar from baseline to 18 months for all 4 strategies. None of the parameters were rated charlie at any recall period. When the 18-month evaluation criteria were pooled by pairs of adhesives none of the 4 strategies resulted in a significantly different number of alfa ratings for any of the criteria compared to the other three strategies. Conclusion: Bonding strategy did not influence the clinical performance of posterior composite restorations under the clinical conditions used in this study.