The limited research that exists about sibling relationships during adulthood has employed primarily sociological variables. Psychological aspects of the sibling relationship were explored in a sample of 35 women and 9 men with a mean age of 59. Subjects completed the California Psychological Inventory, the Scale of Sibling Relationships, and the Semantic Differential of Sibling Relationships with regard to their closest sibling. Data analyses revealed four personality configurations, two of which involved personalities more likely to report sibling rivalry or hostility. Results indicated that people who were hostile toward their siblings were characterized as cautious, rigid, anxious, stereotyped and conventional. Other correlations implied that the perception of a sibling as being jealous of oneself was characteristic of serious, self-assured, outgoing, sincere, stable individuals. Outgoing, creative individuals who valued intellectual achievement reported more cultural activities with their siblings. The final configuration that emerged concerned domestically-related activities shared with siblings; this factor was positively correlated with sociability and well-being. Results support the view that personality variables are important considerations in attempting to understand the quality of sibling relationships, especially in the areas of sibling rivalry and shared activities. (Author/NRB)