The modified Atkins diet is a high-fat, low-carbohydrate treatment for intractable childhood epilepsy. As data suggest that a stricter diet onset can be more effective, we added a ketogenic supplement to the modified Atkins diet during its initial month. Thirty children with intractable epilepsy were prospectively started on the modified Atkins diet in combination with a daily 400-calorie KetoCal shake. At 1 month, 24 (80%) children had >50% seizure reduction, of which 11 (37%) had >90% seizure reduction. There was no significant loss of efficacy during the second month after KetoCal was discontinued. The use of this ketogenic supplement increased daily fat intake and thus the ketogenic ratio (1.8:1 versus 1.0:1 in the modified Atkins diet alone, P = .0002), but did not change urinary or serum ketosis. The addition of a ketogenic supplement to the modified Atkins diet during its initial month appears to be beneficial.