This volume presents the results of the Flourishing Children Project. The study addressed gaps in the research on indicators of positive development of adolescents. Such indicators are essential for the balanced and scientifically sound study of adolescents. Yet measures of many aspects of flourishing are not available, and when they do exist, they are rarely measured in a developmentally appropriate manner for adolescents. In addition, they are often too long for program evaluations and surveys, have not been tested on diverse populations, nor carefully validated as predictors of positive outcomes. The Flourishing Children Project undertook the development of scales for adolescents ages 12-17 for 19 aspects of flourishing covering six domains: flourishing in school and work, personal flourishing, flourishing in relationships, relationship skills, helping others to flourish, and environmental stewardship. This volume describes the four-stage process of developing the scales, including: Reviewing the literature for extant measures for items to test and synthesizing the existing research into consensus definitions for each construct; conducting cognitive testing of items with adolescents and their parents; pilot testing the items; and conducting psychometric analyses.