In industrialized countries, a fundamental shift in child bearing practices has resulted in an increase in the proportion of families with one child. Assumptions contributing to negative ideas about the single child include the notions of the deprivation of positive sibling influences and of debilitating, anxiety-ridden parenting by mothers and fathers of firstborns. Research findings in this area are confounded by a lack of coherent theories, heterogeneous sample selection, poor quality of research designs, and problems confronting new research methodology, such as meta-analysis. Conceptual synthesis is needed to bring this chaotic situation to order. This paper: (1) stresses a need to integrate the effects of significant others with existing theories; (2) underscores the need to assess critical factors affecting the nature and quality of parent-children interaction; (3) suggests that major aspects of school performance and adjustment be considered in the process of detecting the growth and modification of children's personalities; (4) emphasizes the necessity of controlling extraneous factors that contaminate current research; and (5) points to the priority of conducting large-sample studies in single socio-cultural settings before cross-cultural comparisons are made. (RH)