Background Haemodynamic instability is a frequent complication during haemodialysis (HD) treatment. Whether intradialytic haemodynamics is affected by specific antihypertensive treatment is unknown. We hypothesised that angiotensin II receptor blocker (ARB) therapy may affect intradialytic haemodynamic stability and this study describes short and long-term effects of ARB treatment vs. placebo on intradialytic haemodynamic parameters in a cohort of Danish HD patients. Methods Adult HD patients were randomised for double-blind treatment with the ARB irbesartan or placebo using a predialytic systolic blood pressure (BP) target of 140 mmHg. Intradialytic hypotension (IDH) was defined as symptomatic hypotension requiring intravenous fluid administration or preterm ending of the HD session and was recorded for all HD treatments. At baseline, 1 week, 3, 6, 9, and 12 months cardiac output (CO), stroke volume (SV), central blood volume (CBV), total peripheral resistance (TPR), mean arterial BP (MAP), and heart rate (HR) were measured within the first (HDSTART) and last (HDEND) 30 minutes during HD using the Transonic saline dilution technique. Results Eighty-two patients were randomised (placebo/ARB: 41/41). Predialytic systolic BP decreased significantly, but similarly in both groups during the study period. The total number of IDH episodes was (placebo/ARB) 22/25 (P=0.7). Mean HDSTART and mean HDEND CO, SV, TPR, HR, and MAP were stable and similar in the two groups, whereas CBV increased equally and significantly over time. The mean intradialytic haemodynamic response showed decreased CO, SV, MAP, and CBV, whereas HR increased from HDSTART to HDEND. TPR did not change significantly. Overall, this pattern remained stable over time in both groups and there was no significant impact of ARB treatment. Conclusions At equal BP-levels, central haemodynamic parameters during HD were not significantly affected by ARB and IDH episodes were not more prevalent in ARB treated patients.