Most scientific journals practise anonymous peer review. There is no evidence, however, that this is any better than an open system. To evaluate the feasibility of an open peer review system. Reviewers for the British Journal of Psychiatry were asked whether they would agree to have their name revealed to the authors whose papers they review; 408 manuscripts assigned to reviewers who agreed were randomised to signed or unsigned groups. We measured review quality, tone, recommendation for publication and time taken to complete each review. A total of 245 reviewers (76%) agreed to sign. Signed reviews were of higher quality, were more courteous and took longer to complete than unsigned reviews. Reviewers who signed were more likely to recommend publication. This study supports the feasibility of an open peer review system and identifies such a system's potential drawbacks.