We compared cardiovascular outcome between patients with white-coat and sustained hypertension who had previously participated in the Ambulatory Blood Pressure Monitoring and Treatment of Hypertension (APTH) trial. Baseline characteristics, including office and ambulatory blood pressure (BP), were measured during the 2-month run-in period of the APTH trial. During follow-up, information on the occurrence of major cardiovascular events (death, myocardial infarction, stroke and heart failure), achieved office BP and treatment status was obtained. At entry, 326 patients had sustained hypertension (daytime ambulatory BP > or = 140 mmHg systolic and/or > or = 90 mmHg diastolic) and 93 had daytime ambulatory BP below these limits and were classified as white-coat hypertensives. During 2088 patient-years of follow-up (median follow-up 5.3 years), all major cardiovascular events (n = 22) occurred in the patients with sustained hypertension (rate 12.7 per 1000 patient-years, p = 0.02 for between-group difference). Furthermore, multiple Cox regression confirmed that after adjustment for important covariables, daytime ambulatory BP--but not office BP at entry--significantly and independently predicted cardiovascular outcome. After additional adjustment for office BP, daytime ambulatory BP still predicted the occurrence of major cardiovascular events. Although white-coat hypertension was less frequently associated with antihypertensive drug treatment during follow-up, it carried a significantly better prognosis than sustained hypertension.