High blood pressure is both a cause and a manifestation of renal disease. It has an increasing prevalence among renal patients renal function is declining. Blood pressure is not a constant value, but it shows a high intrinsic and extrinsic variability. It is common to find striking discordances between blood pressure values and target organ damage. The average values obtained through ambulatory blood pressure monitoring (ABPM) are better related with cardiovascular morbility and mortality than office measurement, even in renal disease patients. We report the experience with ABPM on 51 renal patients. None of them was on renal replacement therapy. In 7 out of 14 non treated patients ABPM showed clinic hypertension only. Mean age of truly hypertensive patients was higher, but this difference was not significant (normotensive 31.7 +/- 17.1; hypertensive 49.4 +/- 17.9 years, p < 0.1). There were no sex differences (normotensive, 5 males and 2 females; hypertensive, 4 males and 3 females). Three normotensive patients had chronic renal failure, and as did 6 hypertensive patients (p < 0.1). There were no differences in night-time drop either for systolic (normotensive 3.7 +/- 3.5 hypertensive 6.1 +/- 8.9%) or for diastolic blood pressure (normotensive 10.4 +/- 4.7 hypertensive 6.2 +/- 8.9%). Thirty-seven patients who were on antihypertensive drug treatment: 23 (68.2%) showed hypertension after the ABPM and 14 (37.8%) have normal blood pressure values, more over, 4 of these 14 patients showed hypotension. There were neither age differences between the groups (normotensive 49.0 +/- 12.5, hypertensive 51.9 +/- 15.4 years), nor sex differences (normotensive 9 males and 5 females, hypertensive 11 males and 12 females). The prevalence of renal failure was similar (normotensive, 85.7%; hypertensive, 82.6%). Mean night-time drop was not different (SBP, normotensive 6.1 +/- 7.6 hypertensive 7.2 +/- 7.6%; DBP, normotensive 9.0 +/- 8.3 hypertensive 13.5 +/- 7.6%). ABPM is a helpful diagnostic tool in renal disease as in the non complicated essential hypertension patient, both for experimental and for clinical purposes.