The current version of the Declaration of Helsinki states that ‘the benefits, risks, burdens and effectiveness of a new intervention must be tested against those of the best current proven intervention(s) … ’. This wording implies that it is acceptable for patients to be assigned to receive an unproven new intervention and to be denied a best current proven intervention. We assert that patients being invited to participate in controlled trials cannot, ethically, be expected to forego proven beneficial forms of care. Patients being treated in controlled trials should not knowingly be disadvantaged compared with similar patients being treated in usual clinical care, where they have access to beneficial care. In this article, we have tried to separate for discussion ‘the withholding of effective care from trial participants’, ‘informed consent to treatment’, ‘blinding’ and ‘use of placebos’.