Breakfast cereals are usually consumed with milk as a breakfast meal. To meet requirements for amino acids (AA), higher quality proteins are needed to complement the protein in cereals to provide a meal that is adequate in all indispensable AA. The digestible indispensable amino acid score (DIAAS) method used to determine protein quality allows for calculation of the protein value of individual ingredients and mixed meals consisting of several proteins. Values for DIAAS are based on values for apparent ileal digestibility (AID) of AA that are corrected for the basal endogenous loss of each individual AA, resulting in values defined as standardized ileal digestibility (SID). Values for SID of AA are additive in mixed meals because these values are independent of basal endogenous losses. Consequently, it is expected that DIAAS obtained for individual food ingredients are additive in a mixed meal, but data to demonstrate this have not been reported. Therefore, the objective of this experiment was to test the hypothesis that AA in milk complement AA in breakfast cereals to provide a balanced meal and that DIAAS in individual foods are additive in a combined meal.