The approach here proposed to a scientific study of group relations in family and neighborhood is based on the analysis of histories of a number of unmarried mothers. For social study the unmarried mother problem has special interest. First because it deals with a transient, or casual variation upon the family group. Whereas a normal family is a partnership between a strong worker and a socially competent mate for the long care of helpless young, this group precipitated by nature into a? Family status, is yet so disrupted by its lack of sanction in feeling that except for social pressure it disintegrates at once, the stronger parent usually taking his natural advantage to abscond, and the mother seeking the first chance to be relieved of an infant that keeps her in a status of maternity without honor. Second, the fact that illegitimacy makes an abortive family group relates it to several important and complex social questions. It involves at once the marriage laws, the social evil, the causal factors in infant mortality, and the phenomena of mental defect and instability. This complexity and theoretical scope, together with the practical oversight it entails for the detached and somewhat ostracized woman with a baby make illegitimacy a problem that, once grasped, should afford valuable data and a working method for other problems. Adequately to demonstrate the possibilities of the type of analysis here proposed calls for its application to many more social histories. This task I am now entering upon. The first two chapters of this monograph were read before the National Conference of Social Workers in 1921 and 1922, Chapter I having also appeared in the Survey. The first part of this chapter, however, has been entirely rewritten and some te visions made throughout.