Climate and social customs have resulted in a wide variety of animal production systems throughout the world. This chapter reviews the relevance of behavior to production in intensive systems where animals are fed in sheds, milked daily, or given supplementary feed, and in pastoral systems where animals are grazing throughout the year. In intensive systems much of the reduced productivity originates from animals being kept at a high density. In pastoral systems, lowered productivity is most frequently associated with sexual and maternal behavior. The review begins with the recent history of behavioral research, and deals with mother young relations, critical periods, the behavior of young and mature animals in normal and stressful environments, grazing and reproductive behavior, transport, and finally, behavior and selection. Examples have been taken from cattle, sheep, pigs, and poultry and have been considered under the most appropriate heading.