Due to excessive salt and water retention, hypertension often becomes refractory in patients undergoing peritoneal dialysis (PD). Management of high blood pressure (BP) appears to be of particular importance in such patients because of its substantial impact on the patients' prognosis. However, attempts to control hypertension in PD patients have not been successful in most cases. In this regard, the present study aimed to address the adequacy of current antihypertensive therapy for PD patients. A new antihypertensive strategy expected to improve the outcome was tested on the assumption that treatment with either angiotensin converting enzyme inhibitor (ACE-I) or angiotensin receptor blocker (ARB) in the evening together with alpha1-blocker at bed time and long-acting Ca channel blocker (CCB) in the morning might ameliorate BP control associated with morning hypertension. Enrolled in the present study were 40 patients whose BP was evaluated by both office and home measurement. Due to an emerging concern about morning hypertension, home BP measured early in the morning was used for the analysis. Each patient was categorized into the following four groups in accordance with office and home BP: well-controlled, poorly-controlled, white-coat and masked (opposite to white-coat), hypertension. After the observation period, 28 patients with refractory hypertension were allocated to intensive antihypertensive therapy in which ARB or ACE-I previously prescribed in the morning or daytime was shifted to the night. In addition, alpha1-blocker was given at bed time. Furthermore, long-acting CCB and diuretics were shifted to the morning. The patients were then followed up for 4-6 months. The results were as follows: 1) Of the total number of 40 PD patients, systolic hypertension was noted in 50% of cases by office BP and in 80% by home BP. The former was less frequent than the latter (p=0.0047, n=40). Similarly, diastolic hypertension was noted in 20% by office BP and in 45% by home BP. The former was less frequent than the latter (p=0.0045, n=40 by McNemar's analysis). The distribution of BP control categories was well-controlled in 11%, poorly-controlled in 42%, masked hypertension in 39% and white-coat hypertension in 8% when determined by systolic BP. The distribution was well-controlled in 45%, poorly-controlled in 13%, masked hypertension in 34% and white-coat hypertension in 8% of cases when determined by diastolic BP. 2) In 28 patients subjected to the intensive therapy, the control category of systolic BP was changed from 11 to 37% in well-controlled cases, from 42 to 30% in poorly-controlled cases, from 39 to 26% in masked hypertension cases and from 8 to 7% in white-coat hypertension cases. The shift in categories in both poorly-controlled and masked hypertension cases to the better category (well-controlled), was statistically significant (p=0.001, by Wilcoxon's signed rank test). Similarly, the control category of diastolic BP was changed from 45 to 43% in well-controlled cases, from 13 to 15% in poorly-controlled cases, from 34 to 32% in masked hypertension cases and from 8 to 10% in white-coat hypertension cases. There was a tendency for the prevalence of poorly-controlled and masked hypertension to improve to the well-controlled category in response to intensive therapy (p=0.0625, by Wilcoxon's signed rank test). 3) The plasma concentration of plasminogen activator inhibitor (PAI-1)/tissue plasminogen activator (t-PA) complex (total PAI-1 complex) was significantly decreased after intensive therapy (17.3+/-7.8 ng/ml vs. 13.5+/-4.6 ng/ml, n=28, p<0.01 by paired t-test). In contrast, the plasma concentration of t-PA was unchanged even after intensive therapy (4.8+/-3.9 ng/ml vs. 6.2+/-2.9 ng/ml, n=28, ns). These data suggest that home BP obtained in the morning is a useful measure for evaluating morning hypertension in PD patients, most of whom have refractory hypertension categorized as either poorly-controlled or masked hypertension. Intensive treatment with ACE-I/ARB given in the evening along with alpha1-blocker at bed time combined with a diuretic and/or long-acting CCB in the morning is efficacious in controlling the BP of patients with refractory hypertension in PD patients. The link between the reduction in plasma total PAI-1 levels and the intensive therapy may suggest that this therapeutic strategy could prevent thrombotic events associated with morning hypertension in patients on PD.