Purpose: This Review aimed to evaluate the documented clinical success of zirconia-based crowns in clinical trials. Materials and Methods: Electronic databases were searched for original studies reporting on the clinical performance of tooth- or implant-supported zirconia-based crowns including PubMed, Cochrane Library and Science Direct. The electronic search was complemented by manual searches of the bibliographies of all retrieved full text articles and reviews as well as hand search of the following journals: International Journal of Prosthodontics, Journal of Oral Rehabilitation, International Journal of Oral & Maxillofacial Implants and Clinical Oral Implants Research. Results: The search yielded 3,216 titles. Based on pre-established criteria, 42 full-text articles were obtained. While 16 studies fulfilled the inclusion and exclusion criteria, only 3 randomized controlled trials were reported. Seven studies reported on tooth-supported and four on implant-supported crowns, and 5 studies reported on both types of support. Ten studies on tooth-supported and 7 on implant-supported crowns provided sufficient material for statistical analysis. Life table analysis revealed cumulative 5-year survival rates of 95,9% for tooth-supported and 97,1% for implant-supported crowns respectively. For implant-supported crowns the most common reasons for failure were technical (veneering material fractures). For tooth-supported crowns technical (veneering material fractures, loss of retention) and biological (endodontic/periodontic) reasons for failure were equally common. The most common complications for implant-supported crowns were veneering material fractures and bleeding on probing. For tooth-supported crowns the most common complications were loss of retention, endodontic treatment, veneering material fractures, and bleeding on probing. Conclusion: The results suggest that the success rate of tooth-supported and implant-supported zirconia-based crowns is adequate, similar, and comparable to that of conventional porcelain-fused-to-metal crowns. These results are, however, based on a relatively few studies, many that are not controlled clinical trials. Well-designed studies with large patient groups and long follow-up times are needed before general recommendations for the use of zirconia-based restorations can be provided.