To determine the quality of reporting of blinding in randomized controlled trials (RCTs), we evaluated 40 consecutive RCTs published in each of five leading journals. We noted whether authors reported the blinding status of participants, health care providers, data collectors, judicial assessors of outcomes, data analysts, and manuscript writers. Explicit reporting of blinding status occurred in <25% of RCTs for all groups. Eighty-three RCTs, reported as double-blind, provided eight combinations of blinded groups. In conclusion, prestigious journals do not currently report blinding status optimally. To do so, journals should abandon the term "double blind" and explicitly report the blinding status of the groups involved in RCTs. Until such reporting occurs, clinicians will be left with uncertainty about the validity of RCTs that guide their clinical practice. © 2002 Elsevier Science Inc. All rights reserved.