Although the upper arm has the shape of a truncated cone, cylindrical cuffs and bladders are currently used for blood pressure (BP) measurement. The aims of this study were to describe upper arm characteristics and to test the accuracy of a standard adult-size conical cuff coupled to an oscillometric device over a wide range of arm circumferences. Arm characteristics were studied in 142 subjects with arm circumferences ranging from 22 to 45 cm (study 1). In a subset of 33 subjects with the same range of arm circumferences, a rigid conical cuff with standard-size bladder (12.6 × 24.0 cm) and a rigid cylindrical cuff (13.3 × 24.0 cm), both coupled to a Microlife BP A100 device, were tested according to the requirements of the protocol of the European Society of Hypertension (ESH; study 2). Study 1. In all subjects, upper-arm shape was tronco-conical with slant angles ranging from 89.5° to 82.2°. In a multiple linear regression analysis, only arm circumference was an independent predictor of conicity (P<0.001). Study 2. The rigid conical cuff passed all three phases of the ESH protocol for systolic and diastolic BPs. Mean device-observer BP differences obtained with the conical cuff were unrelated to arm circumference. When the rigid cylindrical cuff was used, ESH criteria were not satisfied, and the cuff overestimated systolic BPs in subjects with large arms. BP can be measured accurately with the use of a standard-size rigid conical cuff coupled to a BP A100 device for a wide range of arm circumferences.