Introduction: Treatment guidelines for eating disorders (EDs) recommend individual and group cognitive behavioural therapy (CBT) and individual interpersonal psychotherapy (IPT) as first-line treatments for bulimia nervosa (BN) and binge-eating disorder (BED). This suggests that CBT and IPT have sufficient research evidence and possess specific therapeutic ingredients that will result in a reduction of ED symptoms. There is limited understanding about how different psychotherapies for EDs compare in the treatment of EDs, and whether individual and group psychotherapy modalities are equally effective. Additionally, given that the findings of randomized controlled trials (RCTs) of psychotherapy for EDs are used to develop national treatment guidelines which influence clinician's practice, and that the quality of such studies can influence the magnitude of treatment effects, it is imperative to evaluate the quality of RCTs in order to better interpret the findings. Thus, the overall goals of this dissertation were to systematically and comprehensively evaluate the efficacy of psychotherapy for EDs, and to evaluate and describe the quality of said RCTs. Method: I conducted two meta analyses of direct comparison RCTs of psychotherapy for EDs, including both individual and group psychotherapy. In the third study, I assessed the quality of these RCTs using a tool specifically designed for psychotherapy trials. Results: Results indicated a clear advantage of bona fide psychotherapy over wait-list controls. Bona fide psychotherapy was superior to non-bona fide treatment (treatments that were meant to be effective but were not psychotherapy). These findings were not stable, meaning that when a single study was removed from analyses, results became non-significant. There were no significant differences between bona fide CBT and bona fide non-CBT, with the exception of bona fide CBT resulting in greater reductions in ED psychopathology that was defined by a CBT-model. Group psychotherapy was significantly more effective than wait-list controls. The effects of group psychotherapy and other active treatments (treatments that were meant to be effective, but were not psychotherapy) did not differ on any outcome at post-treatment or at follow-ups. Group CBT and other forms of group psychotherapy did not differ significantly on outcomes at any time point. The mean total quality score for all included RCTs was in line with those reported for RCTs of psychotherapy for depression and anxiety disorders. Several standards of quality were unfulfilled by over half of the included RCTs. More recent RCTs were of higher quality, and higher quality was moderately associated with lower effect sizes. Discussion: Overall, results indicate that there are no differences between the included bona fide non-CBT psychotherapies and bona fide CBT in the treatment of EDs. Whereas the number of trials remains modest, I hope that as more research is conducted, treatment guidelines can be updated, and more evidence-based psychotherapies will be available for EDs. Additional research is needed to evaluate other group psychotherapy approaches, along with CBT, in order to provide more evidence-based treatment options for individuals with an ED. Group psychotherapy appears as effective as other common treatments and is perhaps more cost-effective than the most popular treatment, individual psychotherapy. To improve the quality of RCTs of psychotherapy for EDs, I recommend that researchers address the criteria assessed in quality checklists. Psychotherapy trials should be registered, have a published protocol, and be reported following the Consolidated Standards of Reporting Trials (CONSORT) guidelines. Results from the three manuscripts included in this dissertation will give readers a better understanding of the efficacy of psychotherapy for EDs so they can be better informed when interpreting the findings of studies and recommendations in treatment guidelines. Further, authors of treatment guidelines for EDs, and clinicians' who treat individuals with EDs can consider these findings when updating treatment guidelines and when developing treatment plans for patients.