Introduction: A lack of information exists regarding the efficacy of RetroMTA (BioMTA, Seoul, Korea) directly applied on the pulp in vital pulp therapy. This study was designed to examine the clinical efficacy of RetroMTA compared with ProRoot mineral trioxide aggregate (MTA) (Dentsply Tulsa Dental, Tulsa, OK) for partial pulpotomy. Methods: Partial pulpotomy was performed in 22 healthy human maxillary and mandibular third molars planned for extraction. The teeth were randomly divided into 2 groups (n = 11) and underwent partial pulpotomy with RetroMTA and ProRoot MTA as the control. The teeth were then restored with glass ionomer cement. Clinical and electric pulp tests were performed after 1 and 8 weeks. The teeth were radiographed and extracted at 8 weeks. Histologic sections were prepared and analyzed for pulp inflammation and dentinal bridge formation. Data were analyzed using the Mann-Whitney U test. Results: Clinical examination after 1 and 8 weeks showed no sensitivity to heat, cold, or palpation in the ProRoot MTA and RetroMTA groups. Periapical radiographs taken before the extraction of teeth showed no evidence of periapical pathology. Electric pulp testing revealed no sensitivity. Data comparisons using the Mann-Whitney U test showed no significant difference between the materials with regard to the pulp inflammation type, intensity and extension (P = .3), or bridge continuity (P = .12). However, these data revealed a significant difference between the 2 materials in pulp morphology (P < .05) and bridge thickness (P < .01). Conclusions: This is the first work to evaluate a RetroMTA histologic outcome in partial pulpotomy in human permanent teeth. It shows pulp disorganization, an absence of inflammation, and discontinuous mineralization, which may represent a potential drawback with RetroMTA in this indication.