A national marketing research firm provided a list of 7,014 working telephone numbers in a southwestern city. A total of 499 families agreed to participate in the study. In families with three or more siblings, the first eligible pair was randomly chosen. Appointments were made with the parents to interview their children in their homes. One interview was assigned to each sibling. The delinquency scale consisted of 20 self-report items adapted from Rowe's (1985) instrument of delinquent behavior, with items covering behavior that occurred in the past year. Maternal and paternal affection was assessed with two short scales. Two items assessed parental control. Three subscales were taken from the Sibling Inventory of Differential Experience that assessed peer delinquency, peer achievement, and peer sociability. Two academic scales assessed value on achievement and parental encouragement of academic work. Four personality traits were assessed using scales from Buss and Plomin's (1984) EAS Temperament Survey. Fourteen items from Elliott's normlessness scale were used to form a deceitfulness scale. Eight rebelliousness items were drawn from Smith and Fogg's (1979) 24- item rebelliousness scale. Three factors were extracted from 15 explanatory variables. All three factors were statistically associated with delinquency, but the first factor extracted dominated in terms of variance explained. This first factor had loadings from variables in conceptually diverse domains (for example, family and peer relations, school success, and personality). A question for delinquency theory is why diverse explanatory variables load primarily on one factor, if theories postulate multiple and complex social and individual influences. 3 tables, 1 figures, and 25 references