The authors' supposition is that these stalkers express a deviant pattern of heterosexual pair formation associated with several biological and cultural variables, including a specific brain system for romantic attraction and specific patterns of abnormal attachment. The authors advance five hypotheses regarding the neurobiology of the stalker. First, stalkers may have a different magnitude or ratio between activities of central dopamine and serotonin than normals, producing in the stalker more energy, dysphoria, vigilance, and tenacity in the pursuit of a love object than normals. Second, research on the attachment patterns among stalkers suggests that their bonding is insecure, inferring that their attachment biochemistry varies from that of normal individuals with secure attachments. Third, the affective nature of stalking violence suggests that the stalker has at times a gross lack of impulse control. Fourth, stalking, under some circumstances, may be a manifestation of a compulsion that could have a biochemical origin. Fifth, although stalking is typically not highly sexualized, it is aggressive, suggesting that testosterone may play a role in stalking behavior. 103 references