Sixty-six boys who were members of gangs are responsible for this book. They told me the stories of their gang life and I wrote them out in the form illustrated in Chapter II. I showed these stories to President G. Stanley Hall, who asked me to present them in the Pedagogical Seminary, where an article appeared in June, 1905. These original stories of Boys’ Gangs and Boy Leaders later became the basis for a series of lectures on Boy Problems. In revising my material for book publication, many interesting criticisms by parents, teachers, and social workers, in various sections of the country have been consciously or unconsciously incorporated into it. I have found a wide interest in and demand for such a book as this—bearing upon the group psychology of boyhood—and a lamentable scarcity of readable literature on the subject.