Purpose: This study retrospectively evaluated zirconium oxide posts with either direct resin composite cores or indirect glass-ceramic cores after several years of clinical service. Materials and Methods: One hundred forty-five endodontically treated teeth in 88 patients were restored with zirconium oxide posts; 87 teeth were restored with direct composite cores, and 58 were restored with Empress cores prior to crowning. Seventy-nine posts with direct composite cores in 52 patients and 34 posts with glass-ceramic cores in 19 patients were reevaluated clinically and radiographically after a mean clinical service of 57.7 months and 46.3 months, respectively. Results: Periodontal probing depths remained on a healthy clinical level, and esthetics were judged excellent for the majority of teeth in both groups. In the group with direct composite cores, no failures were observed in the 79 posts that were reevaluated. In the group with indirect glass-ceramic cores, three failures were observed after 42, 43, and 55 months of clinical service. All failures were due to loss of retention. In a best-case scenario posts that could not be reevaluated were considered successful, and in a worst-case scenario they were considered failures; respective success rates were 100% and 91% in the direct group and 95% and 53% in the indirect group. Conclusion: The observed clinical success of zirconium oxide posts with direct composite cores suggests that this method of post-and-core reconstruction is clinically promising. Zirconium oxide posts with indirect glass-ceramic cores displayed a significantly higher failure rate and a high dropout rate that precludes valid conclusions.