OBJECTIVES: Adjudication committees (ACs) are recommended in randomized controlled trials (RCTs) to standardize the assessment of events. We aimed to assess the reporting and functioning of ACs (synonyms: clinical event committees, endpoint committees) in clinical trials. STUDY DESIGN AND SETTING: We searched five high-impact-factor medical journals for reports of RCTs with clinical event endpoints published between January 1, 2004 and December 31, 2005. RESULTS: ACs were reported in 33.4% of the 314 reports of RCTs. ACs were reported in 29.6% of trials with low risk of misclassification (i.e., "hard" main outcome), in 47.5% of trials with medium risk of misclassification (i.e., subjective main outcome and intervention delivered in a blinded fashion) and in 31% of trials with high risk of misclassification (i.e., subjective main outcome without intervention delivered in a blinded fashion). Selected cases to be adjudicated consisted largely of events identified by site investigators (93.3%). Data provided to the AC were reported for 47.4% of ACs. CONCLUSION: Reporting of ACs is not fitted to the risk of biased misclassification. Important aspects of the functioning of ACs are insufficiently reported or raise methodological issues. We propose some recommendations for planning and reporting ACs in clinical trials.