Objective: Changes in the occlusal marginal adaptation of computer-machined inlay restorations were assessed over 3 years. Method and materials: Each of 21 patients received two Cerec 9Vita Mark II) two- or three-surface restorations, with margins entirely in enamel, placed using two of four luting agents: a homogeneous microfilled resin composite, a fine hybrid composite, a realtively coarse hybrid composite, and an encapsulated glass-ionomer cement. Replicas of the restorations were made at baseline 6 months or 1 year (93% of original restorations), 2 years (79%), and 3 years (83%). The percentage of continuous margin on the occlusal margin was evaluated for the enamel-luting agent and luting agent-porcelain interfaces using a scanning electron microscope. Results: Mean continuous margin values were high for all groups at the enamel-luting agent interface; there were no significant differences among the luting agents. For each luting agent, the percentage of continuous margin decreased significantly at the luting agent-porcelain interface over 3 years; differences among the luting agents at 3 years were not significant (Kruskal-Wallis test). After 3 years, the wear of the luting agents was significantly different. The least wear occurred with the microfilled resin composite; the coarse hybrid composite showed the most wear. Conclusion: The occlusal margins of Cerec inlays exhibited consistently high-quality adaptation at 3 years. The microfilled resin composite luting agent was more wear resistant than the hybrid composites and the glass-ionomer cement.