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.