We conducted a retrospective study between 1997 and 2000 with 200 participants in the Children in the Community Study at their mean age of 29 (range: 27–31 years). Participants completed detailed narrative interviews about their transition to adulthood and described monthly levels of partner conflict that had occurred between ages 17 and 27. Data from these interviews were used to investigate the developmental trajectory and predictors of conflict in romantic relationships. Multilevel growth models showed that partner conflict increased between ages 19 and 25 and then declined slightly. Parental divorce, low parental socioeconomic status, being an only child, being divorced, being married, cohabiting, and having biological offspring were associated with elevated partner conflict. Different patterns of association between these variables and partner conflict were observed in men and women.