OBJECTIVE: To determine the accuracy of the SpaceLabs 90207 ambulatory blood pressure monitor for measurement of systolic and Korotkoff phases IV and V diastolic blood pressures in children aged 6-18 years. DESIGN: Monitor evaluation was performed using the 1990 British Hypertension Society (BHS) protocol, adapted for use in children. METHODS: Three SpaceLabs 90207 monitors were evaluated according to the five phases of the 1990 BHS protocol: observer training and assessment; before-use interdevice variability assessment; in-use (field) assessment; after-use interdevice variability assessment; and device validation. Outcome was classified according to the criteria from the BHS (1990) and Association for the Advancement of Medical Instrumentation (AAMI) protocols. RESULTS: During in-use assessment, the monitor failed to achieve the required 70% valid readings on four of 25 recording days. On three of four failed days, kinked tubing errors were noted, possibly caused by excess tubing length. After adjustment of tubing length to body size, criteria were satisfied on 24 additional recording days. During validation, the monitor achieved BHS grade C for systolic blood pressure and satisfied AAMI criteria with a mean difference of 5.0+/- 6.4 mmHg. The monitor received grade D for Korotkoff phase IV and V diastolic blood pressure and failed to satisfy AAMI criteria with a mean difference of -7.2+/- 11.0 mmHg for Korotkoff phase IV and 0.8+/-11.1 mmHg for Korotkoff phase V. CONCLUSION: The SpaceLabs 90207 monitor satisfied the minimum accuracy criteria for measurement of systolic, but not diastolic, blood pressure in children aged 6-18 years.