Objective: The aims of this prospective clinical study were (1) to evaluate the clinical performance of Signum composite inlays over a 3-year period; (2) to investigate the clinical efficacy of composite inlays in premolars versus molars; and (3) to evaluate differences between 1- or 2-surface inlays and multisurface inlays. Method and Materials: One hundred thirteen composite inlays were placed in 30 patients by a clinician. All the inlays were made by the same laboratory technician using only one composite material (Signum, Heraeus Kulzer). All the restorations were bonded with a 3-step bonding system and a composite luting cement. The restorations were assessed after placement by a clinician who had not been involved with the placement of the restorations, in accordance with the modified US Public Health Service criteria. Results: Three of the 113 experimental restorations had to be replaced; the total failure rate was 2.6% after 3 years. At baseline, 88.5% to 100% of the inlay restorations were rated as excellent (Alpha). Statistically significant (P .05) differences were observed during the study for surface roughness, anatomic form at the margin, marginal integrity, and inlay integrity. The comparison of the clinical outcome of inlays in premolars versus molars and with 1 or 2 surfaces versus multisurfaces showed no significant differences, except for the parameters anatomic form at the margin and marginal integrity. Conclusion: Composite inlays demonstrated a very high success rate (97.4%) after 3 years. Neither the size of the restorations nor the tooth type significantly affected the clinical outcome of the restorations. Keywords: composite inlay, composite resin, indirect restoration, posterior teeth