Objectives: The accuracy of blood pressure measuring devices is of prime importance and should be validated before devices are used clinically. We carried out an independent evaluation of the OSCAR 2 oscillometric ambulatory blood pressure monitor (SunTech Medical model 222) according to the European Society of Hypertension International Protocol. Methods: Adult subjects were recruited from patients and staff at The James Cook University Hospital, Middlesbrough, UK. Nine sequential same-arm blood pressure measurements were taken alternating between simultaneous readings by two independent, trained observers using mercury sphygmomanometers and the device operated by a third observer. In phase one, 15 subjects participated (five in each of the low, medium and high blood pressure ranges) with 18 subjects participating in phase two. Data from 33 subjects (11 in each of the three blood pressure ranges) were analysed for systolic (19 male, 14 female, mean age 56.0 years) and for diastolic (17 male, 16 female, mean age 51.1 years) blood pressure. Results: The OSCAR 2 passed the first phase of the validation process. In phase 2.1, the OSCAR 2 monitor had 71 readings within 5 mmHg, 86 within 10 mmHg and 94 within 15 mmHg for systolic blood pressure (SBP) and 72 readings within 5 mmHg, 88 within 10 mmHg and 96 within 15 mmHg for diastolic blood pressure (DBP). Mean (± SD) differences between observers and device were 0.9 ± 2.3 mmHg for SBP and - 0.5 ± 2.3 mmHg for DBP. In phase 2, 24 subjects had at least two of the differences within 5 mmHg and three subjects had no differences within 5 mmHg for SBP while for DBP 25 subjects had at least two of the differences within 5 mmHg and two subjects had no differences within 5 mmHg. Conclusions: The OSCAR 2 passes all requirements for validation by the International Protocol and can be recommended for clinical use in an adult population.