Assessing Animal WelfareWhen evaluating how housing affects the welfare of pregnant sows, it is important to be clear about what is meant by animal welfare. Commonly expressed concerns include the following: 1) animals should function well in the sense of being healthy and thriving; 2) animals should feel well, especially by prevention of serious pain, hunger, fear, and other forms of suffering; and 3) animals should be able to live in a manner consistent with the nature of their species. 1 Task Force members recognized that scientists, including veterinarians, approach animal welfare from different viewpoints and attribute various degrees of importance to each of these concerns on the basis of their education, training, experience, and personal values and the perspectives, morals, and ethical constructs of the society in which they live and work. [2][3][4][5] The ways in which other segments of society interpret animal welfare are likewise diverse. A study 6 conducted in The Netherlands found that producers tended to believe that health and normal biological function were evidence of good animal welfare, whereas consumers tended to focus on the animal' s ability to live a reasonably natural life. A sampling of quotations by ethicists and social critics identified suffering and other affective states as central concerns. 7 Although the degree of importance attributed to each of these elements may vary, Task Force members agreed that no assessment of animal welfare is complete unless all elements are considered. It is not satisfactory, for example, to judge the welfare of an animal on the basis of its physical health without regard for whether it is suffering or frustrated or to conclude that an animal that can engage in species-typical behavior has a good state of welfare without also carefully evaluating its health and physiologic function. In recognition of the need for a comprehensive approach, physiologic function, behavior, physical health, and production indices were used to evaluate the effects and appropriateness of the use of gestation stalls, compared with other systems, for housing pregnant sows. Because ethical perspectives may affect how scientific data are