When can a clinical trial be called 'randomized'?

It is widely recognized that, in the context of the evaluation of medical interventions, randomized clinical trials constitute the gold standard. This is because randomization tends to balance both measured and unmeasured baseline characteristics, allows for masking, and provides a basis for inference. It is understandable, then, that investigators would wish to utilize this methodology whenever it is feasible to do so. Unfortunately, come studies are labeled as randomized when in fact they are not. These studies then receive more credibility, and influence medical practice, more than they deserve to. After reviewing the benefits of randomization, paying particular attention to the specific aspects of randomization that confer each benefit, we will explore the issue of what constitutes a randomized study. Published by Elsevier Science Ltd.