In 21 patients, epilepsia partialis continua (EPC) was an early symptom of nonketotic hyperglycemia and occurred during an initial phase of hyponatremia and mild hyperosmolality. EPC persisted for an average of 8 days, and its duration correlated predominantly with the degree of hyponatremia. Depression of consciousness and cessation of seizures occurred with increasing severity of hyperglycemia and hyperosmolality. In 9 patients, EPC was the first symptom leading to the diagnosis of diabetes mellitus. Four patients died of serious associated illness. The majority of the patients had evidence of a localized structural cerebral lesion. Metabolic disturbances including hyperglycemia, mild hyperosmolality, hyponatremia, and lack of ketoacidosis contribute to the development of EPC in areas of focal cerebral damage.