If randomized controlled trials (RCTs) are to fulfill their potential to allow health care providers to make informed inferences about the validity of the trials upon which they base their clinical practice, then the reporting of key methodological factors must improve. The revised Consolidated Standards for Reporting Trials (CONSORT) were developed to improve the suboptimal reporting of RCTs. We aimed to determine the extent to which RCTs report key methodological factors included in the revised CONSORT recommendations following publication of these recommendations. We conducted an observational study of RCTs published between July 2002 and June 2003 in 5 leading general medicine journals. We determined the proportion and 95% confidence intervals of RCTs that reported sequence generation, allocation concealment, randomization implementation, blinding status of participants, health care providers, outcome assessors, and data analysts, sample size justification, method of analysis (e.g. intention-to-treat), and a participant flow diagram. We included a total of 253 RCTs. RCTs reported: sequence generation 80% (95% CI 75-80%), allocation concealment 48% (95% CI 42-54%), randomization implementation 55% (95% CI 49-61%), blinding status of participants 40% (34-46%), health care providers 17% (95% CI 13-22%), outcome assessors 47% (95% CI 41-53%), data analysts 15% (10-19%), sample size justification 83% (95% CI 78-87%), method of analysis 87% (95% CI 83-91%)), and participant flow diagrams 86% (95% CI 82-90%). Although reporting of some CONSORT recommendations is high, reporting of several essential recommendations remains suboptimal. Authors need to comply with and journals need to enforce reporting of the revised CONSORT recommendations.