Over the past decade, emotion regulation (ER) has gained significant attention. This book details the development of the Adolescent Emotion Regulation Questionnaire (AERQ), which involved testing the validity of well-known theoretical premises of emotion regulation within the structure of a measure of emotion regulation for adolescents. The items were designed to measure ER strategies in cognitive, behavioral, physiological, and social response domains; intensity or duration emotional features; and pleasant or unpleasant emotional valances. The 80 item measure was administered to 364 adolescents between the ages of 12 17 in Greater Edmonton. Confirmatory factor analysis did not support the hypothesized structure based on well-known premises of ER theory. An exploratory factor analysis revealed a 4 factor model that distinguished between pleasant and unpleasant emotional valances; cognitive and physiological response domains within the unpleasant emotional valance; as well as a complex social factor. Convergent and divergent validity was supported. Although logical in nature, existing premises of ER theory are neither practical nor sustainable considering these new developments.