To determine the accuracy of the UA-85X (UA-851, 852, 853, 854, and 855) device developed by the A&D company. Device evaluations were performed using the protocol of the European Society of Hypertension (ESH). Monitor performance was assessed in relation to patients' age, arm circumference, and systolic and diastolic blood pressures (BPs). The device was assessed in two different samples according to ESH requirements, which are based on four zones of accuracy differing from the mercury standard by 5, 10, 15 mmHg, or more. The UA-85X passed all three phases of the protocol for systolic BP and diastolic BP. Mean BP difference between device and observers was -0.3+/-4.4 mmHg for systolic BP and -2.7+/-4.8 mmHg for diastolic BP. These passed the Association for the Advancement of Medical Instrumentation standard requirements. In multivariable analyses, systolic BP discrepancies between device and observers were related to age (P=0.03) and diastolic BP discrepancies were related to diastolic BP level (P<0.001). These data show that the UA-85X satisfies the recommended ESH and Advancement of Medical Instrumentation accuracy levels for both systolic BP and diastolic BP.