The article describes a 20-year longitudinal study of body weight, dieting, and disordered eating in women and men. Body weight increased significantly over time in both women and men. However, women's weight perception and dieting frequency decreased over time, whereas men's weight perception and dieting frequency increased, and disordered eating declined more in women than in men from late adolescence to midlife. In both women and men, changes in weight perception and dieting frequency were associated with changes in disordered eating. In addition, adult roles such as marriage and parenthood were associated with significant decreases in disordered eating from late adolescence to midlife in women, whereas few associations were observed in men. Despite different developmental trajectories, women demonstrated more weight dissatisfaction, dieting, and disordered eating compared with men across the period of observation.