Anorexia nervosa translates to nervous loss of appetite and it is a disorder characterized by low body weight, a fear of weight gain, and an indifference to the symptoms of the disorder. Anorexia nervosa is present in about one percent of the population and mainly afflicts women. Our knowledge on why some persons develop anorexia nervosa is limited, which hinders the development of treatment, diagnostics, and preventive measures. In the ANGI-study we aim to identify underlying biological and environmental factors that cause anorexia nervosa. The results of this research will increase our understanding of the disorder and in the long term we hope that is will lead to more effective treatment and improve diagnostics. We estimate that there are over 40 000 individuals in Sweden who have suffered from anorexia nervosa at some period in their lives. We endeavor to give everyone who is willing an opportunity to participate in this international research project.