ObjectiveTo determine the impact of self-monitoring of blood pressure values (BPS) as compared with office blood pressure measurements (BPO) on the progression of diabetic nephropathy.DesignLong-term, follow-up cohort study.Subjects and methodsHypertensive, type 1 diabetic patients with overt diabetic nephropathy were investigated. Patients initially participated in a hypertension treatment and teaching programme including extensive advice on blood pressure self-monitoring. Self-monitoring and office blood pressure values were continuously assessed during the entire follow-up period. Progression of diabetic nephropathy over the study period was individually assessed as the mean decline of glomerular filtration rate (GFR) per patient per year. Baseline and follow-up parameters were included in stepwise multiple regression analyses with the decline of GFR per year as the dependent variable.ResultsSeventy-seven type 1 diabetic patients (37 women, 40 men) were followed for a mean period of 6.2 ± 2.8 years (mean ± SD; range 2–12) resulting in a total of 481 patient-years. During the follow-up period, mean BPO decreased from 166/95 at baseline to 154/89 mmHg during follow-up, and mean BPSfell from 159/93 to 138/83 mmHg. The mean decline of GFR was 4.1 ± 5.6 ml/min per year. Loss of kidney function was significantly correlated with proteinuria, blood pressure and glycosylated haemoglobin values. In the multiple regression analyses, BPSpredicted the loss of renal function better than BPO(R2= 0.52 versus 0.42). The simple correlation between BPSand GFR decline was higher compared to BPOand GFR (r= −0.42; P < −0.0001 versus −0.33; P < 0.004).ConclusionBlood pressure self-monitoring values are a better predictor of progression of diabetic nephropathy when compared with office blood pressure measurements.