The personal adjustment of 457 large family siblings, as made by the informants in 58 families, shows the following results.1. Approximately 2 of 3 siblings were reported as well adjusted, one of 4 was medium in his adjustment, and one of 9 was poorly adjusted.2. A larger proportion of male siblings than of female were well adjusted, and of medium adjustment.3. In-between children show higher rates of good and medium adjustment than do the first and last born. Of the latter 2 groups, the last-born have the better record.4. First-born children have the poorest record and fourth-born by far the best record.5. Poorly adjusted children, considered collectively, tend to be grouped in homes in which the father is domineering, or the mother is ineffective and irresponsible, in which the children are exploited, and where health problems abound.Abstract Teaser