Some trajectories indicate that youths improve their behavior over time. The findings support the position that behavior over time reflects a change in psychological and environmental characteristics and that a substantial portion of adolescents with clinically significant youth self-report (YSR) total scores improve over time. Specifically, over time the high improving group had substance use and depression drop, family satisfaction increase, fewer parents with mental health or addiction problems, fewer peers using substances, and a decrease in neighborhood problems and stressors. Little is known about behavioral trajectories across adolescence, and less is known about the potential predictors of different trajectories. This study addresses that knowledge gap in a population of American Indian youths; a group that has higher rates of addictions and mental health problems than many other groups. A total of 401 urban and reservation American Indian adolescents were interviewed yearly from 2001 to 2004. Tables, figure, references