Patients with a blunted or absent nocturnal blood pressure (BP) drop may be subject to increased risk for target organ damage. In this 3-year longitudinal case-control study we tested the hypothesis that an association exists between a reduced or absent night-time fall in BP and a future decline of kidney function in renal hypertensive patients. The case subjects were 48 hypertensives with renal insufficiency, divided into two groups according to the presence (dippers: n 20) or absence (non-dippers: n 28) of a nocturnal diastolic BP decline greater than 10% of daytime values, detected by ambulatory BP monitoring. At the baseline evaluation the two groups did not differ with respect to age, sex, body weight, office systolic and diastolic BP, mean daytime ambulatory BP, creatinine clearance, 24 h proteinuria. In the ambulatory BP profiles over a 3-year follow-up the nocturnal reductions of systolic and diastolic BP in the dippers were 14% and 15%, respectively, vs 7% and 5% in the non-dippers (p = 0.002/0.003). The non-dippers had a faster rate of creatinine clearance decline than the dippers (0.37 +/- 0.26 vs 0.27 +/- 0.09 ml/min/month; p = 0.002). Urinary protein excretion increase was higher in the non-dipper group than in the dipper group (993 +/- 438 vs 691 +/- 222 mg/24 h; p = 0.009). This longitudinal study suggests that the non-dipping pattern of ambulatory BP can be associated with a faster progression of renal insufficiency in renal hypertensives and that a proper nocturnal BP control is an additional aim of antihypertensive therapy.