A 20-year longitudinal study examined the stability and change in attachment security from infancy to early adulthood. Sixty white middle-class infants were assessed in the Ainsworth Strange Situation at 12 months, and 50 were recontacted 20 years later and interviewed using the Berkeley Adult Attachment Interview (AAI). Overall, 72% of participants retained the same attachment classification (secure vs. insecure). Negative life events, such as parental loss, divorce, illness, psychiatric disorders, and abuse, were significant factors in changes. Fifty-six% of those with negative life events changed classifications, compared to 28% of those without. These results support Bowlby's hypothesis that attachment security can be stable yet open to change. The study also examined the role of early experiences in shaping attachment patterns. Bowlby's theory emphasizes the importance of early experiences in shaping attachment representations. The study found that attachment security in infancy was significantly related to AAI attachment security 20 years later. Hierarchical regression analyses showed that stressful life events were significantly related to changes in attachment classification, particularly for secure infants becoming insecure. However, stressful events did not significantly affect changes in insecure infants. The study highlights the importance of measuring attachment security and the role of real-world experiences in shaping attachment patterns. It also underscores the need for further research into the mechanisms underlying stability and change in attachment. The study's findings support the value of the secure base concept in understanding attachment relationships across the lifespan. The results also suggest that middle-class samples may reflect more than just inherent stability of attachment security, as factors such as social support and low rates of negative experiences may contribute to stability. The study emphasizes the importance of examining attachment stability in diverse populations and the mechanisms of change in close detail.A 20-year longitudinal study examined the stability and change in attachment security from infancy to early adulthood. Sixty white middle-class infants were assessed in the Ainsworth Strange Situation at 12 months, and 50 were recontacted 20 years later and interviewed using the Berkeley Adult Attachment Interview (AAI). Overall, 72% of participants retained the same attachment classification (secure vs. insecure). Negative life events, such as parental loss, divorce, illness, psychiatric disorders, and abuse, were significant factors in changes. Fifty-six% of those with negative life events changed classifications, compared to 28% of those without. These results support Bowlby's hypothesis that attachment security can be stable yet open to change. The study also examined the role of early experiences in shaping attachment patterns. Bowlby's theory emphasizes the importance of early experiences in shaping attachment representations. The study found that attachment security in infancy was significantly related to AAI attachment security 20 years later. Hierarchical regression analyses showed that stressful life events were significantly related to changes in attachment classification, particularly for secure infants becoming insecure. However, stressful events did not significantly affect changes in insecure infants. The study highlights the importance of measuring attachment security and the role of real-world experiences in shaping attachment patterns. It also underscores the need for further research into the mechanisms underlying stability and change in attachment. The study's findings support the value of the secure base concept in understanding attachment relationships across the lifespan. The results also suggest that middle-class samples may reflect more than just inherent stability of attachment security, as factors such as social support and low rates of negative experiences may contribute to stability. The study emphasizes the importance of examining attachment stability in diverse populations and the mechanisms of change in close detail.