Protocols to determine the accuracy of noninvasive blood pressure monitors have been published by the Association for the Advancement of Medical Instrumentation, the British Hypertension Society, and the European Society of Hypertension (ESH). We compared the statistical basis for each of these protocols. Although the Association for the Advancement of Medical Instrumentation and British Hypertension Society protocols require a minimum of 85 participants, the ESH protocol requires only 33 participants. The reduced sample size results in a reduction in statistical power from 98 to 70%, which brings into question the applicability of the ESH (International) protocol.