The present study was designed to assess the relationship between the presence of focal brain aedema and serum concentrations of atrial natriuretic peptide (ANP) or brain natriuretic peptide (BNP) in patients with subarachnoid haemorrhage (SAH). Serum levels of ANP and BNP were measured at six different time periods (Day 1, 2, 3, 4 to 7, 8 to 14, and 15 to 25) in 61 SAH-patients. Focal brain aedema, which was caused by an intracerebral haematoma associated with SAH or surgical complications, was found in eight SAH-patients by means of consecutive CT scans. The mean serum ANP and BNP levels in patients with focal brain aedema were significantly higher than those in patients without focal brain aedema between Days 4 and 14. These findings suggest that focal brain aedema may have some role in the pathogenesis of an excessive secretion of ANP and BNP during the subacute phase of SAH.