Sixty-three adult patients with newly diagnosed partial seizures underwent MRI of the brain including hippocampal quantitation. Seventy-six percent of patients had normal MRI findings, 10% had hippocampal sclerosis (HS), and 14% had MRI abnormalities other than HS. Patients with HS had a worse early prognosis than patients with other MRI findings with respect to seizures. The extent of hippocampal damage appeared to be an important mediating factor in frequency of seizures, secondary generalization, and resistance to antiepileptic drug treatment. Because MRI provides prognostic information and can alter management for the individual patient, high-resolution MRI should be performed in all patients with newly diagnosed partial seizures.