To characterize precursors and trajectories in the development of borderline personality disorder (BPD), anonymous internet surveys were administered to parents about their BPD offspring and non-BPD siblings. Questions covered aspects of probands' lives from pregnancy through young adulthood. BPD offspring were identified through both lifetime clinical diagnoses and diagnostic criteria embedded within the survey. We report on 234 female offspring meeting strict criteria for BPD, and 87 non-BPD female siblings. Parents of daughters with BPD describe the presence of affective symptomatology starting in infancy, including significant differences from non-BPD probands in moodiness. These affective symptoms persist after infancy, and are Joined by interpersonal difficulties that manifest themselves in toddlerhood and childhood. By adolescence, difficulties with impulsivity, aggression, acting out, and self-destructive behaviors dominate the profile.