In 14 patients with ophthalmoplegia plus Tc-99m hexamethylpropylene amineoxime (HMPAO) brain SPECT imaging was performed. Three patients showed bilateral parieto-occipital hypoperfusions, and two patients had left parietal defects (one with an additional right temporal lesion). Two patients presented with occipital hypoperfusions and one with a distinct hypoperf usion in the medial part of both frontal lobes. Hypoperfusion of the visual cortex might result from permanently decreased input from the degenerated retina. The hypoperfusion in the visual cortex and in other regions alternatively might reflect direct central nervous system (CNS) involvement due to neuronal degeneration or to impaired vascular function caused by morphologically changed mitochondria in smooth muscle and endothelial cells. The data suggest CNS involvement in ophthalmoplegia plus with abnormalities of cerebral blood flow similar to those found in other mitochondrial encephalomyopathies.