ntroduction The optimal BP target in older hypertensives is unclear with concerns that adverse effects from hypotension may occur with intensive treatment. The effects of BP lowering on cerebral blood flow (CBF) are unclear. We used MR arterial spin labelling to determine the effect of usual and intensive BP lowering on CBF in older subjects with hypertension. Methods 37 patients >70 yrs with systolic BP > 150 mmHg on one or no BP lowering drugs were recruited from primary care and randomised to usual (<140/85 mmHg, n=17) or intensive (<130/80 mmHg, n=20) treatment regimens. Grey matter cerebral blood flow (CBF) was measured with 3T MR using a FAIR ASL sequence with Gradient Echo Planar Imaging at baseline and 12 weeks. results BP at baseline and 12 weeks were; usual 155/84 vs. 140/79 mmHg and intensive 149/87 vs. 123/70 mm Hg. CBF was unchanged in the usual treatment group (73 vs. 76 ml/100gm/min, p=NS) but increased in the intensive group (81 vs. 74ml/100gm/min, p<0.01). CBF change in the intensive group was greater than in the usual group; 7+11 (mean SD) vs. -3+9; p<0.01. conclusions Intensive BP lowering in older hypertensives increases cerebral blood flow. These data suggest that hypertension shifts the autoregulatory CBF curve rightwards and downwards, that intensive BP lowering may not increase the risk of syncope in older people with hypertension, and may protect the brain against the development of white matter lesions if white matter perfusion is similarly increased.