Lack of an effective treatment for spontaneous intracerebral haemorrhage (ICH) is partly because the mechanism of neuronal damage in ICH is not fully understood. Animal experiments have shown that there is a zone of ischaemia and oedema around the haematoma which can be reduced by early evacuation of the mass lesion. We set out to study Cerebral Blood Flow (CBF) changes in patients with ICH. We present data on 13 patients (mean age 60). SPECT scans were performed within 48 hours of ictus and 4-7 days later. Four patients had surgical evacuation of the clot; 9 were managed conservatively. The ratio of uptake of the isotope in the cerebral hemisphere containing the haematoma to the isotope uptake in the contra-lateral (un-affected) cerebral hemisphere was taken as an index of perfusion of the affected cerebral hemisphere. The perfusion index of the affected hemisphere improved between the first and the second scans in all the surgically treated patients; in the conservatively managed group, it was worse in 6 patients, the same in 1 and very slightly better in 2. There was an overall mean improvement of 3.87% in the surgical group, and an overall mean deterioration of 3.61% in the medical group. This data suggests that surgical evacuation of the clot may improve perfusion in the ipsilateral cerebral hemisphere in ICH. It underlines the importance of a prospective randomised trial to assess the value of surgery in patients with ICH. The Surgical Trial in Intracerebral Haemorrhage (STICH) is currently underway worldwide. We also describe the application of Difference Based Region Growing (DBRG) to SPECT image analysis. This method overcomes the difficulties posed by 1) the presence of a mass lesion and 2) surgical evacuation of haematoma.