Randomized controlled trials of public health interventions are often complex: practitioners may not deliver interventions as researchers intended, participants may not initiate interventions and may not behave as expected, and interventions and their effects may vary with environmental and social context. Reports of randomized controlled trials can be misleading when they omit information about the implementation of interventions, yet such data are frequently absent in trial reports, even in journals that endorse current reporting guidelines. Particularly for complex interventions, the Consolidated Standards of Reporting Trials (CONSORT) statement does not include all types of information needed to understand the results of randomized controlled trials. CONSORT should be expanded to include more information about the implementation of interventions in all trial arms.