Objective: To examine the potential for mealtime boluses of biphasic insulin aspart 70 (BIAsp70); 70% rapidacting fraction and 30% intermediate-acting fraction, in reducing the subsequent increase of blood glucose (BG) after a meal rich in protein and fat.Materials and Methods: The subjects were 25 children with type 1 diabetes mellitus (T1DM) who were currently on multiple daily injections. They were divided into two groups based on lunchtime insulin use, i.e. 20 using rapid acting insulin (group Ra) and 5 using BIAsp70 (group BIAsp70). The BG profiles before and up to 6 hours after taking the two types of lunch were compared between the two groups.Results: The postprandial changes of the BG concentrations (Δ%) 1, 2, 3 and 6 hours after Japanese-style meals in the Ra group were 14, 15, 10 and −8%, and those in the BIAsp70 group were −8, 62, −11 and −30%. The Δ% reduction after 3 and 6 hours were greater in the BIAsp70 group than in the Ra group. On the other hand, the Δ% after the protein-and fat-rich meals in the Ra group after 1, 2, 3 and 6 hours were 97, 63, 49 and 34%, compared with 69, 43, 40 and −24%, respectively, in the BIAsp70 group. BG decreased to below the preprandial level and the Δ% was negative after 6 hours in the BIAsp70 group compared with the Ra group.Conclusions: Mealtime boluses of BIAsp70 might be useful to control postprandial glycemia after 3 hours or more, in children with T1DM, especially after a protein-and fat-rich meal.