We evaluated the ictal and interictal single photon emission computed tomography (SPECT) of 9 patients with West syndrome (WS). In this group, we noted two clear patterns of cortical hyperperfusion and subcortical hyperperfusion in the ictal SPECT. Both patterns were different from the previously documented ictal patterns for complex partial seizures (CPS) or secondarily generalized seizures. Our results suggest that the tonic spasms of WS do not always have a single neurophysiological basis; e.g., patients with hemihypsarrhythmia and focal hypsarrhythmia did not show ictal hyperperfusion of the lesion with hypsarrhythmia. These findings indicate that the origin of hypsarrhythmia as an EEG feature and the origin of tonic spasms may be different in such patients. In particular, hypsarrhythmia appears to originate from cortical lesions, whereas the subcortical structures may be primarily responsible for the tonic spasms. Our report is the first published study of ictal SPECT in patients with WS.