This study was performed to determine the utility of Tc-99m-HMPAO brain SPECT in evaluating patients with pure photosensitive epilepsy. Methods: Seven patients (2 boys, 5 girls), aged 8 to 15 yr (mean 11.1+/-2.5 yr), were studied. All patients underwent a detailed neurologic examination, interictal and ictal EEGs, CT and/or MRI and SPECT imaging. The baseline SPECT study was performed during the interictal period and the activation study was performed while the patients were having seizures provoked by watching television. Results: The baseline SPECT study showed that six of seven patients had relatively hypoperfused regions in their frontal robes that could involve the neighboring parietal and temporal regions. The activation study revealed that all seven patients had relative hyperperfusion in these brain regions that were relatively hypoperfused in the baseline study. The side-to-side asymmetry indexes for these visually-interpreted rCBF abnormalities ranged from 3% to 6%. Conclusion: The relatively consistent pattern of frontal rCBF alterations suggests that frontal lobe functions were implicated in the evolution of photosensitivity-related seizures in patients with pure photosensitive epilepsy.