Most hypertensive dialysis patients are currently treated with angiotensin converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB). Aliskiren, the direct renin inhibitor, has not been specifically studied in peritoneal dialysis patients. The aim of the study was to compare hypotensive effects of aliskiren and ramipril and their influence on serum potassium and inflammatory parameters in hypertensive peritoneal dialysis patients. Eighteen hypertensive patients on chronic peritoneal dialysis were enrolled in an open-label comparative fixed-order study. The patients had been off RAAS blocking drugs for ≥4 weeks prior to an inclusion. At each of 3 study visits (baseline and after each of the treatment periods) blood pressure, serum lipids, potassium, renin, aldosterone, C-reactive protein (CRP) and monocyte chemotactic protein-1 (MCP-1) were measured. After the baseline visit aliskiren was started (150 mg/d) and after 12 weeks replaced with ramipril (5 mg/d) for the next 12 weeks. Blood pressure was 142/88±15/11 mmHg at baseline, 137/84±10/8 mmHg after aliskiren (ns) and 126/81±11/7 mmHg after ramipril (p<0.05 vs baseline and aliskiren). No incidents of hyperkalemia were observed. Plasma renin concentration increased significantly during aliskiren treatment compared to ramipril (227,6±844 vs 58,3±765 pg/mL). CRP was similar after both therapies (8,8±34 vs 8,4±32 µg/mL) but MCP-1 concentration was significantly lower after aliskiren than after ramipril (294,0±172,6 vs 358,9±183,3 pg/mL). Aliskiren 150 mg/day decreases blood pressure less effectively than ramipril 5 mg/day in peritoneal dialysis patients. It does not influence serum potassium. The decrease of MCP-1 concentration after aliskiren treatment may provide an indirect evidence for its blood pressure independent cardioprotective and anti-inflammatory effects.