INTRODUCTION Of the 1,252 infants housed in the Rooming-In Unit! between its

opening and the close of the time for selection of study patients, approximately half came from families belonging to the professional or professional-in-training class. The records of three families were selected for the Seminar on Mental Health and Infant Development from the predominant socio-economic group of the rooming-in families, and from this group only, in the belief that the differences in the children and parent-child relationship would stand out more strikingly against a similarity of background. The three sets of parents were alike in the following respects: They were white, of early American descent, and Protestant. They were aged between twenty-five and thirty. They were college graduates, and the husbands were post-graduate students. The pregnancies were planned; the parents all felt they could afford a family and that they could count on help either from their families or from some other source of income. The mothers were primiparas and the infants were female, born within a few months of each other under similar hospital conditions. The mothers were private patients. They had requested rooming-in and wanted to nurse. The parents lived under comparable conditions in a community of families with similar academic background.