Technical Abstract: Honey bees play an important role in terrestrial ecosystems. Through their pollinating activities, honey bees provide a service that is vital to the diversity and maintenance of wild plant communities and to agricultural production. The western honey bee (Apis mellifera) is arguably the single most valuable insect pollinator to agriculture because their hives can be easily maintained and transported to pollinator-dependent crops. Though there is a great need for managed honey bee colonies, there has been an almost 50% decrease in world honey bee stocks over the last century. Simultaneously there has been a greater than 300% increase in pollinator-dependent crops. Colonies fail for many reasons including starvation, queen failure, diseases, parasites and pests. Pesticides can also cause colony losses. Most recently, a syndrome of unknown etiology called colony collapse disorder (CCD) has caused massive colony losses, especially to commercial beekeeping operations. The following Chapters provide the latest information on factors that undermine the health and survival of colonies. The role of beneficial microbes and bee breeding in maintaining the health and vigor of colonies also are included as these areas have potential to create sustainable solutions to problems of colony health.