Objective: This longitudinal randomized controlled clinical trial evaluated composite resin inlays for clinical acceptability in single- or multisurface preparations and provides a survey of the results up to 3 years. Method and Materials: Twenty-one dental students placed 75 Artglass (Heraeus Kulzer) and 80 Charisma (Heraeus Kulzer) composite resin inlays in Class 1 and 2 preparations in posterior teeth (89 adults). Clinical evaluation was performed at baseline and up to 3 years by two other dentists using modified USPHS criteria. Results: A total of 89.8% of Artglass and 84.1% of Charisma inlays were assessed as clinically excellent or acceptable with predominating Alfa scores. Up to the 3-year recall, five Artglass and 10 Charisma inlays failed mainly because of postoperative symptoms, bulk fracture, and loss of marginal integrity. No significant differences between composite resin materials could be detected at 3 years for all clinical criteria (P > .05). The comparison of restoration performance with time within both groups yielded a significant increase in marginal discoloration (P .05) and deterioration of marginal and restoration integrity (P .05) for both inlay systems. However, both changes were mainly effects of scoring shifts from Alfa to Bravo. No significant differences (P > .05) were recorded comparing premolars and molars. Small inlays showed significantly better outcome for some of the tested clinical parameters (P .05). Conclusion: Clinical assessment of Artglass and Charisma composite resin inlays exhibited an annual failure rate of 3.4% and 5.3% that is within the range of published data. Indirect composite inlays are a competitive restorative procedure in stress-bearing preparations. Keywords: clinical study, composite resin, inlays, longevity, USPHS criteria