This study examined whether patients with borderline personality disorder and controls with other personality disorders remember their childhoods differently with respect to separation difficulties, evocative memory, temperamental factors such as frustration tolerance and mood reactivity, and onset of symptoms. Two hundred and ninety patients with borderline personality disorder and 72 with other personality disorders were assessed using an instrument to rate memories of separation difficulties, temperamental problems, and onset of symptoms before age 18. Patients with borderline personality disorder remembered more difficulties with separation between ages 6 and 17 years, more mood reactivity and poorer frustration tolerance between ages 6 and 17, and the onset of more symptoms (most prominently sadness, depression, anxiety, and suicidality) before age 18 than did patients with other personality disorders. The groups did not differ in reports of evocative memory before age 18. These results indicate that many of the features of adult patients with borderline personality disorder may initially appear during childhood and adolescence and that these features may be used to differentiate borderline from other personality disorders.