The measurement of the blood pressure of corpulent persons often leads to over-estimation. We have therefore compared, for 10 over-weight women (body mass index = 38.04 +/- 1.32 kg/m2) whose average age was 54 +/- 4 years, the blood pressure figures obtained by the invasive method (humeral artery) with values measured automatically by the Bard-Sentron apparatus (B.S.) on the one hand, and the mercury sphygmomanometer (S. Hg) on the other hand. The cuff (bladder = 25 X 12.5 cm) was placed on the same side of the forearm. (table; see text) We have compared the values obtained by invasive and Bard-Sentron methods (I), invasive and mercury sphygmomanometer methods (II), and Bard-Sentron and mercury sphygmomanometer (III) respectively. (Table: see text). The correlations are excellent for the systolic blood pressure, as the Bard-Sentron over-estimates by 5.5 p. 100. They are not so good for the diastolic blood pressure as the Bard-Sentron over-estimates by 33 p. 100. The mercury sphygmomanometer over-estimates the diastolic blood pressure by about 43 p. 100. For conclusion: The blood pressure measurement taken on the forearm of corpulent persons by auscultation or by automatic methods is reliable for the systolic blood pressure, but the diastolic blood pressure is largely over-estimated.