This report describes two cases of cortical dysplasia in patients with intractable epilepsy: the first case presents a 12-year-old male with a simple partial seizure of his left arm (case 1), while the second case presents an 8-year-old female with a complex partial seizure (case 2). Magnetic resonance images showed high signal intensity on T2-weighted and fluid attenuated inversion-recovery images in the cerebral cortex of right frontal convexity in case 1 and in the medial temporal lobe and anterior amygdala in case 2. The latter lesion showed focal contrast enhancement. Light microscopy revealed perivascular clustering of small round cells accompanied by dysplastic neurons in the second to sixth layers of the cerebral cortex. The perivascular small cells had uniformly round nuclei and plump, ground-glass-like cytoplasm. These cells closely apposed each other and were adhered to the capillaries. In case 2, a ganglioglioma was also found in the amygdala. Immunohistochemistry revealed that the perivascular small cells were vimentin and focally S-100 protein positive, but were negative for glial fibrillary acid protein, synaptophysin, neurofilament protein, microtubule-associated protein 2, neuronal nuclei antigen, nestin, carbonic anhydrase II, myelin basic protein, CD68, factor VIII, cytokeratin, epithelial membrane antigen, α-smooth muscle actin, CD20, CD45 and CD45RO. These data suggest that this is a previously undescribed form of cortical dysplasia comprising dysplastic neurons and immature perivascular cells of possible oligodendroglial or meningothelial lineage. We suggest the term cortical perivascular satellitosis be used to describe this lesion.