The SpaceLabs 90202, a non-invasive ambulatory blood pressure recorder for the measurement of 24 hr blood pressure, was assessed according to the standard of the Association for the Advancement of Medical Instrumentation (AAMI) and the grading criteria of the British Hypertension Society (BHS) protocol were applied to the results. Two observers measured BP simultaneously in the same arm with the SpaceLabs 90202 and a standard mercury sphygmomanometer at 4 mmHg deflation steps in 85 subjects [age range 22-79 years, BP range 96-212 mmHg (systolic) and 52-134 mmHg (diastolic)]. The mean difference was -2 +/- 5 mmHg (systolic) and -2 +/- 5 mmHg (diastolic). The mean difference (+/- SD) between observers was 1 +/- 3 (systolic) and -2 +/- 3 (diastolic). The SpaceLabs 90202 fulfills the criteria of the AAMI standard (5 +/- 8 mmHg) and a B grading for both systolic and diastolic pressure is achieved with the BHS criteria.