AIMS: To determine the relationship between blood pressure (BP) measurement in the clinic and self-monitored blood pressure (SMBP); and to evaluate the accuracy of self-reported data in patients with Type 2 diabetes treated intensively for hypertension. METHODS: Seventy subjects had baseline and 1-week follow-up clinic BP measured using an Omron 907 automated device. During a contemporaneous 14-day period these subjects measured their BP at least four times each day using an Omron IC semiautomatic portable monitor which, unknown to them, contained an onboard memory capable of storing BP with corresponding time and date. RESULTS: There was no significant difference between mean clinic and mean self-monitored BP. Correlations between clinic BP and SMBP were r=0.61 (P<0.0001) for systolic BP and r=0.69 (P<0.0001) for diastolic BP. Clinic BP classified 56 subjects as uncontrolled hypertension (BP > or = 130/80 mmHg, adjusted for diabetes) and 14 subjects as controlled hypertension. Using World Health Organization-International Society of Hypertension criteria for SMBP (> or = 125/75 mmHg), 55 cases of clinic classified uncontrolled hypertension were confirmed, resulting in 98% sensitivity. Clinic and SMBP agreed in one case of controlled hypertension, resulting in 7% specificity. For all subjects, the median percent of values exceeding SMBP criteria for controlled hypertension was systolic 92% and diastolic 70%. Self-reporting precision averaged 89+/-10% (range 45-100%); under-reporting was 25+/-16% (ranging from 0 to 56%) and over-reporting was 12+/-15% (ranging from 0 to 46%). The overall logbook mean was not significantly different from the downloaded data from the Omron IC(R) monitors. CONCLUSIONS: SMBP was able to identify 13 patients with uncontrolled hypertension who, by clinic BP measurement, had been classified as controlled.