To the Editor.— Drs Kramer and Shapiro 1 give some valuable guidelines to improving the quality of research in their article, "Scientific Challenges in the Application of Randomized Trials," in the Nov 16, 1984, issue ofThe Journal. However, I'm afraid they perpetuate some of the misunderstandings concerning the nature of the placebo effect and its role in controlled clinical trials. Two errors are found in their discussion of blinding and unblinding: "If the active treatment leads to improvement in the patient's symptoms or signs, he or his physician may become unblinded... although such a bias cannot create an efficacious effect." The two errors are these: (1) The placebo effect is not simply a function of whether the patient or physician "knows" or "correctly guesses" whether the patient belongs in the control or active treatment group. (2) A placebo can create an efficacious effect, as has been amply documented. 2