The purpose of the study was to evaluate the loss of nocturnal (N) decline in blood pressure (BP) in type II treated hypertensive diabetics. The study concerned 36 hypertensive diabetics 59 +/- 10 years old, 20 men and 16 women, with poor metabolic control (HbA1C: 9.6 +/- 3%), without dysautonomia; 14 had macroproteinuria and/or microalbuminuria (mu alb) (< 30 micrograms/min). An ambulatory BP monitoring (Spacelabs 90207) was performed in all patients. Left ventricular mass index (LVMI) and E/A were determined by Doppler-echocardiography. Two groups (G) were individualized: G1 (n = 17), with a normal circadian rhythm (diurnal and N.BP significantly different); G2 (n = 19) with a loss of N decline in systolic (S) and diastolic (D) BP or both; and compared to non diabetic treated hypertensive controls (G3). There was no difference neither in LVMI (125 +/- 43 g/m2), E/A (0.7), 24 h-mean (M) BP in the three groups, nor in HbA1C levels and mu alb occurrence in G1 and G2. Mean N.SBP and mean N.DBP were more closely related to LVMI in G2 than in G1 and G3. [table: see text] Half of these hypertensive diabetics, with bad metabolic control, have an altered circadian BP pattern; the prognostic value of nocturnal BP, related to LVMI despite the antihypertensive treatment, is suggested.