We studied brain perfusion in 19 patients with infantile neuronal ceroid-lipofuscinosis (INCL), aged 13 months to 11 years, using 99mTc-HMPAO single photon emission computed tomography (SPECT). SPECT findings were compared with clinical manifestations and MRI findings. The typical SPECT findings at an early stage of INCL were bilateral anterior frontal, posterior temporoparietal and occipital hypoperfusion. Initially cerebral hypoperfusion was localized and symmetrical, whereas atrophic findings were more generalized. Reduction in cerebellar perfusion appeared later, as did cerebellar atrophy. Progression from mild to severe cerebral and cerebellar hypoperfusion was rapid, corresponding to the clinical progression. However, the perfusion of deep grey matter structures (basal ganglia and thalami), although atrophic on MRI, was often well preserved up to the terminal stage. Severe perfusion defects in INCL, which appeared approximately at the age of four, were associated with grave clinical manifestations and neuropathologic findings. Particularly, the early SPECT perfusion abnormalities may assist in the differential diagnosis between INCL and other neurode-generative diseases.