We present in some detail what constitutes normal behavior, or mental health, among teenagers. Our data are based on the results of a specially devised psychological questionnaire by one of us (D.O.). This questionnaire has been shown to reliably distinguish mentally healthy from psychiatrically disturbed populations. Results are presented across three decades (1960s, 1970s, and 1980s), across genders, and across the high school years. A conceptual framework is presented to help the clinician working with adolescents to understand the fluctuation in psychopathology among youth. Adolescent density in the total population is shown to be a significant factor in determining the rate of disturbance among teenagers. Our research findings demonstrate that the rate of behavioral disturbance among adolescents is the same as in other parts of the life cycle. The clinician working with adolescents tends to underestimate the severity of adolescent problems because of the near-universal belief that all adolescents undergo "adolescent turmoil." We have found that adolescents who are experiencing turmoil need professional help.