This part introduction presents an overview of the key concepts discussed in the subsequent chapters. The part reviews of the contributions of anthropological research to health, covering the areas of cultural definitions of health and illness, social organization in health and illness, and environmental effects on health. It aims to develop two important issues with respect to health differentials in modern societies—psychosocial factors in susceptibility to illness and factors related to differences in utilization of health care services. The part suggests that differences in patterns of perceiving events and in coping styles can explain the difference in outcomes among persons facing the same pattern of stress. It examines the topic both with respect to patient support by family and community and to social organization of medical practitioners. The part explains the influence of psychosocial factors on susceptibility to physical illness.