OBJECTIVE: To test the SpaceLabs Medical 90217 ambulatory blood pressure monitor for compliance with The Association for the Advancement of Medical Instrumentation's standard and a modification of the British Hypertension Society (BHS) protocol. METHODS: The study concerned 85 subjects aged 17-88 years with various arm circumferences and ranges of blood pressure. Resting casual blood pressure was 135 +/- 24/76 +/- 14 mmHg (mean +/- SD). For each subject nine readings of the 90217 device were compared with auscultatory reference readings of two independent observers who used a dual stethoscope. The measurements were performed with subjects standing, sitting and supine. The manual reference readings were alternated with the 90217 monitor's readings. RESULTS: Average differences between manual (average of recordings by two clinicians) and automated readings were -5 +/- 4.3/0.6 +/- 4.6 mmHg (seated), 0.0 +/- 6.0/-1.8 +/- 4.7 mmHg (standing) and -1.6 +/- 5.1/-0.7 +/- 5.1 mmHg (supine).CONCLUSIONS: The device meets the Association for the Advancement of Medical Instrumentation's standard. Comparing the results with the modified BHS protocol, it was found that the device earned the highest BHS grade of 'A' both for systolic and for diastolic blood pressures.