It is not uncommon for a beekeeper to observe in a colony the presence of one or two cells of what appears to be American foulbrood and on the next examination discover that the cells have apparently been cleaned of all visible remains of the disease. In a majority of such cases, the disease will appear at a later date with greater severity while in a minor number of instances, it will not recur. In the latter cases the questions arise as to whether it was American foulbrood and, if so, was it a less virulent strain than usual or did the colony actually manifest a certain amount of resistance to the disease.