One hundred ninety patients were considered for surgical treatment of uncontrolled partial seizures. Twenty-seven (15%) had intracranial mass lesions detected during preoperative evaluation. Seizures were present for a mean of 10 years. Sixty percent of the patients had prior negative radiologic studies. The lesions included 19 neoplasms and 8 non-neoplastic structural (non-atrophic) lesions. Refractory simple partial seizures and a changing neurologic examination were more commonly associated with neoplasms. Treatment included biopsy and radiation, mass resection, or subtotal lobectomy. Although any form of treatment gave better seizure control, patients undergoing subtotal lobectomy had more than 95% reduction in seizures.