Background: Little information is available on the reproducibility of nocturnal variations in blood pressure in type 2 diabetic hypertensive patients. Objective: We aimed to compare the intrasubject short-term reproducibility of a nocturnal non-dipping pattern and the prevalence of cardiac and extracardiac signs of target organ damage, in a group of type 2 diabetic hypertensive patients and in an age/gender-matched group of non-diabetic hypertensive subjects. Methods: Thirty-six treated hypertensive patients with long-lasting type 2 diabetes (&rt; 10 years duration) consecutively attending our hospital out-patient hypertension clinic (group I; mean age, 65 +- 9 years), and 61 untreated non-diabetic subjects with grade 1 and grade 2 uncomplicated essential hypertension, matched for age and gender, and chosen from patients attending an outpatient clinic (group II; mean age, 65 +- 5 years), were considered for this anal. All patients underwent blood sampling for routine blood chem., 24-h urine collection for microalbuminuria, two 24-h periods of ambulatory blood pressure monitoring (ABPM) within a 4-wk period, echocardiog., and carotid ultrasonog. A dipping pattern was defined as a greater than 10% redn. in the av. systolic and diastolic blood pressure at night compared with av. daytime values. Results: A reproducible nocturnal dipping and non-dipping profile was found in 11 (30.6%) and 21 (58.3%) diabetic patients, resp.; while only in four (11.1%) patients was a variable dipping profile obsd. Of the 23 patients with a non-dipping pattern during the first ABPM period, 21 (91.3%) also had this type of pattern during the second ABPM recording. In group II (non-diabetic hypertensive patients), 30 patients (49.2%, P < 0.05) had a dipping pattern, 13 patients (21.3%, P < 0.01) had a non-dipping profile pattern and 18 patients (29.5%, P < 0.01) had a variable dipping pattern. Of the 20 patients with a non-dipping pattern during the first ABPM period, 13 (65.0%) confirmed this type of pattern during the second ABPM recording. Finally, the prevalence of left ventricular hypertrophy (77.7 vs. 41.4%, P < 0.01), carotid plaques (80.5 vs. 38.3%, P < 0.01), carotid intima-media thickening (54.3 vs. 44.0%, P < 0.05) and microalbuminuria (11.1 vs. 2.0%, P < 0.01) was significantly higher in group I than in group II. According to a logistic regression anal., diabetes, left ventricular hypertrophy and carotid plaques were the main independent predictors of the non-dipping (pattern in the overall population. Conclusions: These findings indicate that intrasubject variability of non-dipper pattern is lower in diabetic than in non-diabetic hypertensive patients, that classification of diabetic hypertensive patients as dipper or non-dipper on the basis of a single ABP recording is more reliable than in non-diabetic patients, and that the more frequent and reproducible non-dipping (pattern in diabetic patients is assocd. with a more prominent cardiac and extracardiac target organ damage. [on SciFinder (R)]