The Online journal of current clinical trials
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To investigate the association between trial characteristics, findings, and publication. The major factor hypothesized to be associated with publication was "significant" results, which included both statistically significant results and results assessed by the investigators to be qualitatively significant, when statistical testing was not done. Other factors hypothesized to have a possible association with publication were funding institute, funding mechanism (grant versus contract versus intramural), multicenter status, use of comparison groups, large sample size, type of control (parallel versus nonparallel), use of randomization and masking, type of analysis (by treatment received versus by treatment assigned), and investigator sex and rank. ⋯ Even when the overall publication rate is high, such as for trials funded by the NIH, publication bias remains a significant problem. Given the importance of trials and their utility in evaluating medical treatments, especially within the context of metaanalysis, it is clear that we need more reliable systems for maintaining information about initiated studies. Trial registers represent such a system but must receive increased financial support to succeed.