CRD summary: The authors concluded that topical azelaic acid was an effective treatment for papulopustular rosacea, and was as effective as metronidazole. This was generally a well-conducted review. However, the conclusion about the relative efficacy of azelaic acid and metronidazole was not based on studies included in this review, and its reliability is therefore unclear. CRD commentary: The review question appeared to be clearly defined. However, there was inconsistency between the review question presented in the abstract of the review and the inclusion criteria for eligible comparison therapies reported under 'Study Selection' in the text. The search was extensive, used no language restrictions, and made reasonable attempts to locate unpublished studies; this reduces the possibility that relevant studies were not included in the review. The authors used appropriate methods to reduce bias and error in the study selection, validity assessment and data extraction processes of the review. Appropriate criteria were used for the validity assessment and the results were reported. The decision to employ a narrative synthesis was appropriate in the absence of necessary statistical information in the primary studies. The authors' conclusion as to the effectiveness of azelaic acid, compared with vehicle, was based on studies included in the review and was therefore likely to be reliable. However, their conclusion with respect to the relative efficacy of azelaic acid and metronidazole appeared to be based on the findings of two excluded studies which were not assessed for validity, thus the reliability of this conclusion cannot be determined.