AbstractEvaluations of the efficacy of over‐the‐ounter drugs using ANOVA techniques often misuse multiple comparison procedures. Studies that involve both a placebo control and established drugs as positive controls are especially prone to these problems. The most common mistake involves using a procedure which does not control the experimentwise type I error rate, usually the Duncan procedure or some version of multiplettests. These procedures control comparisonwise type I error rate, but lack the important experimentwise error control.The purpose of this paper is to clarify the issues involved in performing ANOVA followed by a multiple comparison procedure for over‐the‐ounter drug studies involving both placebo and positive c