Stalkers engaging in persistent campaigns of harassment have the potential to cause immense harm to their victims and themselves. Being able to estimate which stalkers are likely to persist longest is important to clinicians dealing with both perpetrators and victims. This study of 200 stalkers investigated characteristics of the stalkers and their behaviour that were associated with increased persistence. Logistic regression models were developed to predict low, moderate, and highly persistent stalking. The results supported previous research indicating that the type of prior relationship between stalker and victim is strongly associated with persistence, with prior acquaintances the most persistent, and strangers least. Being aged over 30, sending the victim unsolicited materials, and having an intimacy seeking or resentful motivation was also associated with greater persistence, as was the presence of psychosis.