This review of the literature on the "only child" indicates that the single child is likely to be oriented more toward adults than towards peers, to be subjected more to an adult culture, to be an achiever who strikes out on his own, and to have a heightened sense of responsibility compared with children who have siblings. Statistics show only children often grow up to be outstanding, but there is a long-standing prejudice against the only child; parents often feel that they have to have a second child to "save" their first. Advantages for parents who have one child are discussed in terms of (1) less financial strain, (2) more freedom, (3) ability to devote time and energy to the child, (4) contribution to zero population growth, (5) avoidance of sibling rivalry, and (6) ability of mothers to realize their own ambitions while enjoying the experience of motherhood. It is concluded that "Oneness" by itself is not a determining factor in how an only child behaves, affecting the child only in the sense that being the eldest, middle or youngest child would affect behavior. (GO)