Summary The ‘placebo effect’ concept is intrinsic to the architecture of the double blind placebo randomised controlled trial (RCT), the oft quoted ‘gold standard’ method of clinical research whose findings are supposed to inform our understanding of the interventions used in clinical practice. The ‘placebo effect’ concept is often used in discussions of both clinical practice and clinical research, particularly when discussing why patients report improvements with complementary and alternative medicines (CAMs). Despite its frequent use, ‘placebo effect’ is a non-sequitur, thus confusion abounds. In routine healthcare patients are not told that they might receive placebo. However, in clinical trials the opposite is true. Telling people that they might receive a placebo really complicates things. The uncertainty invoked by information that a placebo may be given can impact trial recruitment, the delivery of the intervention, and the reporting of outcomes, as can the ‘meaning responses’ invoked by other types of information provided to patients in standard RCT designs. Future CAM research should consider alternative RCT designs that help ensure that participants’ experiences are uncontaminated by ‘meaning responses’ to information that they may receive fake treatments, i.e. placebos.