The authors present diagnostic criteria with which the borderline disorder picture with its fears and defensive strategies can be reliably detected even in preschoolers. Although aggressiveness almost always dominates symptomatic in these children, this serves above all to protect against fear of extermination. Early pathogenic relationship patterns of these children, which distort their experience of reality, can be changed with appropriate treatment strategies. Transmission-focused psychotherapy (TFP) can re-initiate age-appropriate development in children with Borderline Syndrome. Case vignettes illustrate the explanations.