The chapter “The Growth of the City” was presented first as a paper at the meeting of the Sociological Society in Washington, in 1923. It was subsequently printed in the _Proceedings_ of the Society for that year. It is intended to sketch a point of view for the study of the expansion of the urban area and the growth of the urban community, particularly as they are related to the recognized problems, communal and personal, of the city. Professor McKenzie’s paper, “The Ecological Approach to the Study of the Human Community,” was first published in the _American Journal of Sociology_ for November, 1925. It is intended to emphasize the fact that the conceptions and methods of study of plant and animal ecology may be profitably applied to the analysis and description of certain aspects of human society. These three papers, with the classified bibliography by Louis Wirth, represent whatever is novel in the point of view and the methods of study of the urban community, to which this volume is intended as an introduction. Certain of the remaining chapters, including the paper “The Natural History of the Newspaper,” first published in the _American Journal of Sociology_, November, 1923; the paper “Magic, Mentality, and City Life,” presented at the annual meeting of the American Sociological Society, in Washington, D.C., December, 1923; and the brief paper on the “Mind of the Hobo,” first printed under the title “The Mind of the Rover,” in the _World Tomorrow_, September, 1923, will no doubt seem rather remote from the theme of this volume. The justification for including them here is that they suggest lines of observation in a field that students are just now beginning to explore. It seems evident that there is a very definite relation between human intelligence and community organization. Although no specific studies have been made in this field, they should be included, at least prospectively, in the list of problems for further study. The substance of the chapter “Community Organization and Juvenile Delinquency” was presented at the annual meeting of the Recreation Congress, in Springfield, Illinois, October 8–12, 1923, but has not been previously published. The paper “Community Organization and the Romantic Temper” was read at the meeting of the American Sociological Society in Washington, D.C., in 1923, in the section on Community Organization. It was published in the _Journal of Social Forces_, May, 1925. Professor Burgess’ paper, “Can Neighborhood Work Have a Scientific Basis?” was presented at the annual meeting of the National Conference of Social Work, in Toronto, May 1924. An abstract of this paper was published in the _Proceedings_ of the conference for that year. In conclusion, the authors wish to take this occasion to acknowledge their indebtedness to the publishers for using here the papers in the journals mentioned. ROBERT E. PARK