A case of subarachnoid haemorrhage secondary to rupture of an intracranial aneurysm occurring in a patient with new-onset, frank thyrotoxicosis is described. This unusual case highlights the dilemma of whether to continue beta-blockers such as propanolol for frank thyrotoxicosis, or whether to assign higher priority to maintaining adequate cerebral perfusion pressure in established ischaemic deficit due to vasospasm. In a complicated case such as this, the Maudsley Mentation Test score and perfusion CT scanning are two useful adjuncts for the early detection and evaluation of the course of ischaemic deficit.