This study is a preliminary attempt to investigate whether internal or external pubertal changes and whether social or biological factors are more likely to be associated with negative affect. About 100 white girls aged 10-14 years were given a physical examination, had blood drawn, and filled out the Youth Behavior Profile and a life-events checklist. Negative affect increased during the most rapid rises in hormone levels; however, hormones accounted for only 4% of the variance in negative affect. Pubertal status and timing were not associated with negative affect. In contrast, social factors accounted for more variance than hormonal pubertal factors alone (8%-18%), as did the interaction of negative life events and pubertal factors (9%-15%). Results are discussed in terms of what hormonal activation effects are most likely to be found, the meaning of such effects for subsequent behavior, and the interaction of biological and social events.