This prospective, birth cohort study addressed three questions: Which individual and family-of-origin characteristics predict the age at which young men make the transition to fatherhood? Do these characteristics predict how long young men live with their children? Are individual differences in the amount of time fathers spend living with their children associated with the fathers' psychosocial characteristics in young adulthood? Individual and family-of-origin characteristics were assessed from birth until age 15, and contemporaneous characteristics were assessed at age 26. By age 26, 19 percent of the 499 study men had become fathers. Those who had experienced a stressful rearing environment and history of conduct problems were more likely to become fathers at an early age and to spend less time living with their children. Of those who experienced no risk factors, fewer than 10 percent had become fathers by age 26, versus more than 60 percent of those who experienced 5 risk factors. Fathers who lived apart from their children reported the most social and psychological difficulties in young adulthood. Findings point to individual and family-of-origin characteristics that might be targeted to delay fatherhood and increase levels of paternal involvement. (Contains 60 references.) (SM)