PURPOSE: The aim of this study is to evaluate the effect of serum sodium level on seizure features of benign convulsions with mild gastroenteritis. METHODS: We assessed 31 patients with benign convulsions with gastroenteritis at Soonchunhyang University Cheonan Hospital, from March 2010 to December 2012. The patients' data including sex, age on visit, semiology, frequency and duration of seizure, laboratory findings, seizure onset after gastroenteritis, EEG findings and brain MRI findings were retrospectively reviewed. RESULTS: Thirteen boys and 18 girls were involved in the study. Their mean age was 19.7+/-12.7 months. Twenty two patients (71.0%) visited hospital from November to March in terms of monthly distribution. The seizure types were generalized tonic clonic seizures (61.3 %), generalized tonic (29.0%), atonic (6.5%) and partial seizures (3.2%). The duration of seizures was mostly within 5 minutes. The onset of seizures from gastroenteritis was 1 to 3 days. Stool rotavirus antigen test were positive in 3 of 20 patients. Electroencephalography was performed in 22 patients, in which only four patients showed generalized delta activities without sharp wave/spike discharge. Brain MRI was performed in 16 patients and only one patient had small venous malformation in the right frontal lobe. Seven out of 31 patients had mild hyponatremia. There were no significant differences in the semiology, frequency and duration of seizures between the group with mild hyponatremia and normal group. CONCLUSION: The study showed that mild hyponatremia did not affect seizure features of benign convulsions with mild gastroenteritis. However, further studies are needed.