BACKGROUND: Melatonin modulates central nervous system neuronal activity. We compared the melatonin levels of patients with febrile and afebrile seizures during and after seizure with those of healthy controls. METHODS: We enrolled 59 individuals with afebrile and febrile seizures (mean age, 6.09 +/- 4.46 years) and 28 age-, sex-, and weight-matched healthy children. Melatonin levels were measured near the time of a seizure (0 to 1 hour) and at 12 and 24 hours post-seizure, and control melatonin levels were measured from a single venous blood sample. RESULTS: Plasma melatonin levels increased during seizures in the study group (P < 0.001). Post-seizure plasma melatonin levels were significantly lower in the study group than in the control group (P < 0.05). Plasma melatonin levels did not differ between patients with afebrile seizures who had and had not used antiepileptic drugs. Daytime (8 AM to 8 PM) and nighttime (8 PM to 8 AM) post-seizure melatonin levels were not significantly different. CONCLUSIONS: Melatonin levels were lower in pediatric patients prone to seizures than in healthy children and increased during seizures. Further research is needed to test the role of melatonin in the pathophysiology and treatment of epilepsy. (C) 2016 Elsevier Inc. All rights reserved.