Diffuse and focal changes in glucose utilization and abnormal cerebral cortical perfusion were found in West syndrome by PET and SPECT investigations. In this study 99mTc-HMPAO SPECT was performed on seven patients with symptomatic West syndrome several months after the onset of the spasms. Regions of interest of the cerebral cortex and cerebellum were delineated by an automated computer program and cortical/cerebellar ratios of the HMPAO uptake in the patients were compared to those of controls. The basal ganglia/cerebellar ratios were compared after manual placement of regions of interest. Significantly reduced perfusion was found in the bilateral anterior, mid frontal and perisylvian cortex, and in the left posterior frontal and temporal areas. Well localized, focal changes in the cortical perfusion were not found and the perfusion in the basal ganglia proved to be normal. These abnormalities in the cortical perfusion may reflect a pre-existing brain pathology together with an encephalopathy due to the hypsarrhythmia and infantile spasms.