The detection of vasospasm plays an important role for the definition of the strategy of treatment in patients with subarachnoid hemorrhage (SAH). Besides the invasive contrast angiography, the non-invasive 99m-Tc-HMPAO brain perfusion SPECT and transcranial Doppler sonography (TCD) are recently used for this purpose. For the investigation of the possibilities of the last two methods, comparative studies were performed in 29 SAH patients in the subacute phase of the disease. In the detection of regional brain ischaemia the sensitivity of the SPECT study was 90%, the specificity was 28% and the accuracy was 50%, the corresponding values of TCD were 82%, 71% and 75%. In patients, in whom chronic neurological symptoms, or morphological abnormalities could be excluded, the specificity of the SPECT study was 67% at unchanged sensitivity. Based on the results it is concluded, that the brain perfusion SPECT and the TCD investigation are useful methods for the detection of vasospasm after SAH. The combination of the two methods is recommended for the correct diagnosis of vasospasm in SAH. Further investigations are necessary to clarify the prognostic impact of the result of these investigations.