It has been shown that mice and rats treated with antimuscarinic drugs, scopolamine or atropine, after fasting for 48 h develop convulsions soon after refeeding. The present study was performed to evaluate whether mice also develop convulsions after being deprived of food for 1-24 h. The effect of day-night fasting on the development of convulsions was also determined in 12-h deprived animals. Mice were deprived of food for periods of 1, 2, 3, 6, 9, 12, 18, 24, and 48 h. Animals fasted for 12 h during the day or night were deprived of food at 08:00 or 20:00 h, respectively. At the time of testing, animals were treated with intraperitoneal (i.p.) saline or 3 mg/kg scopolamine. Twenty minutes later, they were given food and allowed to eat ad lib. All animals were observed for 30 min for the incidence and onset of convulsions. Fasted animals treated with scopolamine developed clonic convulsions after food intake. Incidence of convulsions was significant in 2-, 3-, 12-, 18-, 24-, and 48-h deprived animals. Convulsions observed after deprivation of food for 12 h during the day or at night were almost similar in both regimens. Our results indicate that food deprivation itself, rather than its duration, seems to be the principal factor in the development of these convulsions.