Objective: To clinically evaluate computer-aided design/computer-aided manufacturing (CAD/CAM)-fabricated molar endocrowns after 6 months and 1, 2, and 3 years of clinical service. Materials and methods: 289 patients with 321 molars (267 patients with one endocrown, two patients with two endocrowns, and ten patients with three endocrowns) exhibiting extensive coronal loss of substance participated in the study. Endocrown preparations were scanned, and endocrowns designed and machined with the Cerec CAD/CAM system. The endocrowns were adhesively seated using a composite luting agent, and assessed using clinical United States Public Health Service (USPHS) criteria at baseline, 6 months, and 1, 2, and 3 years after placement. Patient satisfaction was evaluated using a questionnaire. Results: None of the 289 endocrowns failed during the observation period. The high clinical rating criteria (97.2%) and the high satisfaction percentage (98.0%) remained practically unchanged (P > 0.05) throughout the follow-up assessments at 6 months and after 1, 2, and 3 years. Conclusion: Monolithic zirconia endocrown restorations represent an effective method of restoring posterior teeth after root canal therapy. Based on the short-term observation period of the present study, monolithic zirconia endocrowns can be considered a reliable restoration for endodontically treated molars with extensive coronal loss of substance. Keywords: monolithic zirconia endocrowns, CAD/CAM fabrication, clinical short-term rating, patient acceptance