We report a girl presenting with drug-refractory myoclonia and generalized tonic-clonic seizure (GTCS) on awakening who, initially, was misdiagnosed as having juvenile myoclonus epilepsy (JME) before insulinoma was detected. Many conditions may mimic or cause epileptic seizures, including psychiatric and movement disorders, cardiac arrhythmias and metabolic abnormalities. Toxic and metabolic causes are potentially curable, are refractory to antiepileptic drugs, and may be fatal if untreated. Insulinoma is a rare and treatable cause of hypoglycemic seizures which might be misdiagnosed as intractable epilepsy. Case report In May 2001 a 13-year-old girl was referred to the hospital because of GTCS on awakening. The family history was unremarkable and her personal history revealed one simple febrile seizure at age 3 years. One month before admission two episodes of confusional states were reported which lasted 5 and 30 min and were characterized by unresponsiveness and psychomotor slowing. 1 Fig. 1 Ictal EEG on awakening: generalized low-amplitude spike with simultaneous registration of myoclonic jerks of the hands and legs. Although the EEG pattern is not so typical for JME, together with the history and the clinical symptoms this EEG seemed compatible with this diagnosis  5 9 MENIN Surgery was performed 5 months later (March 2002) in Moscow and two insulinomas were revealed by intraoperative US: one located on the superior-posterior surface between the head and body (diameter 2.5 cm) and the other on the anterior surface of the pancreas (diameter 0.7–0.9 cm). Before the surgery, US and MRI disclosed only one lesion. Both insulinomas were removed in toto and the endocrine pancreas was suppressed by Sandostatin (octreotide) for 4 days. Histology confirmed the diagnosis of two benign beta-cell adenomas. The patient fully recovered, remained seizure free during the next 4 years, has a current weight of 62 kg (75th centile), and is mentally normal. Discussion 2 10 4 9 4 10 10 4 4 3 4 4 6 8 1 3 5 7 1 3 5 Conclusions The combination of seizures and episodic confusional states should prompt the search for hyperinsulinism, especially when the episodes occur in fasting states and when they are refractory to antiepileptic treatment. Inappropriately high insulin with low blood glucose is diagnostic; this constellation has to be investigated resolutely (e.g., by the classic 72-h fasting test) but with caution under strict clinical and chemical monitoring. Timely diagnosis of an insulinoma is of paramount importance to prevent sequelae for such patients.