Fourty-four multiple publications of 31 comparative trials of nonsteroidal anti-inflammatory drugs in rheumatoid arthritis were examined for mutual agreement. Thirty-two of the papers were published in the same language as the primary version. Important discrepancies were seen in 14 trials, involving description of the study design in two, exclusion of protocol violators in two, inconsistency in the number of effect variables in five, in the number of side-effects in five, and in the significance level in one. In three articles the conclusion became more favourable for the new drug with time. Only half of the trials had the same first author and number of authors. For six trials, multiple publication was difficult to detect. Adherence to the manuscript guidelines published by the International Committee of Medical Journal Editors should diminish the risk of inflated meta-analyses, reference lists and curricula vitae, and inexplicable discrepancies in articles based on the same data.