Objectives: To maintain high treatment quality it is important to evaluate orthodontic treatment results using objec - tive methods. Outcome assessments allow private practitioners and university students to evaluate their results and raise the level of treatment outcomes. The aim of this study was to assess the orthodontic treatment outcome in a post-graduate orthodontics program in the University of Valencia (Spain) and to determine whether the treatment outcome is related to several factors as gender, age at start of the treatment, treatment duration, treatment method, extraction-non extraction treatment and cooperation needed. Material and Methods: A sample of 50 patients treated in the post-graduate clinic was randomly selected. Pre- treatment and post-treatment study casts have been assessed by the Peer Assessment Rating (PAR index). The in - fluence of various factors: gender, age at start of the treatment, treatment duration, treatment method, extraction-non extraction treatment, cooperation needed and number of students finishing each case, were statistically analyzed. Results: According to the PAR index, orthodontic treatment reduced the malocclusion in a mean point reduction of 21.4 (CI 95% 18.7-24.1) and a mean percentage reduction of 80.5% (CI 95% 75.9-85.1). The total of the cases improved, 44% of the patients were in greatly improved category. Conclusions: None of the variables studied influenced significantly the treatment outcomes regarding the PAR. Ba - sed on the general classification criteria of the index, the results showed that the patients received a high standard treatment.