It is debated whether white-coat (WCHT) and masked hypertension (MHT) are at greater risk of developing a sustained hypertensive state (SHT). In 1412 subjects of the Pressioni Arteriose Monitorate e Loro Associazioni Study, we measured office blood pressure (BP), 24-hour ambulatory BP, and home BP. The condition of WCHT was identified as office BP >140/90 mm Hg and 24-hour BP mean <125/79 mm Hg or home BP <132/82 mm Hg. Corresponding values for MHT diagnosis were office BP <140/90 mm Hg, 24-hour BP > or =125/79 mm Hg, and home BP >or =132/82 mm Hg. SHT was identified when both office and 24-hour BP means or home BP were over threshold values and normotension was under the threshold value. Subjects were reassessed 10 years later to evaluate the BP status of the various conditions defined previously. At the first examination, 758 (54.1%), 225 (16.1%), 124 (8.9%), and 293 (20.9%) subjects were normotensive, WCHT, MHT, and SHT subjects, respectively. At the second examination, 136 normotensives (18.2%), 95 WCHT (42.6%), and 56 MHT (47.1%) subjects became SHT. As compared with normotensives, adjusting for age and sex, the risk of becoming SHT was significantly higher for WCHT and MHT subjects (odds ratio: 2.51 and 1.78, respectively; P<0.0001). Similar results were obtained when the definition of the various conditions was based on home BP. Independent contributors of worsening of hypertension status were not only baseline BP, but also, although to a lesser extent, metabolic variables and age. Subjects with WCHT and MHT are at increased risk of developing SHT. This may contribute to their prognosis that appears to be worse as compared with that of normotensive subjects.