In the pre-awakening hours, diastolic blood pressure (DBP) is normally at its lowest, and diastolic hypotension is a risk factor for cardiac ischemia. We investigated pre-awakening DBP values and its predictors in treated hypertensive patients who underwent ambulatory blood pressure monitoring. The pre-awakening period was defined as the 3-h period ending 1 h before awakening (most frequently 03:00-06:00). In 269 included subjects, office DBP was 86.4±12.0 mm Hg, 24-h DBP was 78.6±9.6 mm Hg, mean pre-awakening DBP was 70.3±10.9 mm Hg, and trough pre-awakening DBP was 62.5±11.2 mm Hg. Half of the patients (51%) had a mean pre-awakening DBP <70 mm Hg, and 14% had <60 mm Hg. Trough pre-awakening DBP <60 mm Hg was seen in 36% and <50 mm Hg in 12% of patients. Office DBP was the most important predictor of mean and trough pre-awakening DBP (both beta=0.4; P<0.001), and of pre-awakening DBP <70 mm Hg and <60 mm Hg (both P⩽0.001). Diabetes mellitus was associated with a lower trough pre-awakening DBP (beta=-3.2; P=0.02). Among variables that failed to independently predict low pre-awakening DBP were age, a history of vascular disease, and classes and number of antihypertensive drugs. We found that many hypertensive patients have low DBP in the pre-awakening period. Office DBP is the main predictor of low pre-awakening DBP. Further studies are needed to define the prognostic relevance and potential risks of low pre-awakening DBP.