Growth of larvae of two genetically different lines of the honey bee, Apis mellifera, one resistant and one susceptible to American foulbrood (AFB) disease, was determined in three genetically different nurse colonies. Larval weight of the resistant line were significantly greater than larval weights of the susceptible line from the 48-hr to the 144-hr age when reared in the same colony. Larvae reared in a nurse colony of the susceptible line weighed significantly more at 24-hr to 120-hr ages than genetically similar larvae reared in a colony of the resistant line. Larvae reared in a commercial hybrid nurse colony ranged from intermediate to approximately the same weight as those reared in the susceptible colony. All larvae reached approximately similar weights by 144 hr of age.