The effects upon libraries of the major social changes of the past two decades and the probably future effects of such changes are analyzed in this report, based upon a search of the professional literature, a field survey, and opinion sampling from leaders in the library profession and civic leaders belonging to the National Book Committee. Five principal future responsibilities of libraries include: (1) supporting formal education at all levels, (2) sustaining the increasingly complex operations of the government and the national economy, (3) providing opportunities for continuing self-education and retraining, (4) playing a role in the reintegration of the disadvantaged into society, and (5) providing resources for an informed public opinion and for personal growth. The impact of rapid social change will be to render the library's role more central, requiring vastly increased public support. From an institution with rather general aims which functions somewhat on the margins of our central concerns, the library will increasingly become a part of our essential machinery for dealing with these concerns, especially in core cities. The appendix includes the questionnaires used for the surveys, a summary of the survey results, and a bibliography of 157 items. (Author/JB)