Attachment theory is one of the earliest and most vigorously promoted explanations of the psychological processes that underlie stalking behavior. Insecure attachment has been proposed as impairing the management of relationships, thus increasing the propensity to stalk. The current study explored the parental bonding and adult attachment styles of 122 stalkers referred to a specialist forensic clinic. Stalkers were grouped according to two common classification methods: relationship and motivation. Compared to general community samples, stalkers were more likely to remember their parents as emotionally neglectful and have insecure adult attachment styles, with the degree of divergence varying according to stalker type and mode of classification. In offering support for the theoretical proposition that stalking evolves from pathological attachment, these findings highlight the need to consider attachment in the assessment and management of stalkers. Also emphasized is the importance of taking classification methods into account when interpreting and evaluating stalking research.