Stalking includes obsessional following, domestic stalking, obsessive relational intrusions, and unwanted pursuit behaviors. The intrusion is persistent or has a pattern, has a threatening nature that may result in harm to the target’s body or property, and invokes fear in the target. In this study, relationships with the following characteristics were examined: (1) a dating or intimate relationship; (2) began during high school or college; (3) lasted for at least 1 month; (4) one person made it clear that he or she wanted the relationship to end; and (5) the other person subsequently engaged in intrusive contact that lasted at least 2 weeks. Questionnaires were distributed to 790 undergraduates through several social science courses at 2 medium-sized public universities in the eastern United States. The questionnaire contained basic demographic questions, a section completed by those that had been the target of intrusive contact, and a section completed by those that had initiated intrusive contact. Twenty-four percent of the females and 15 percent of the males had been the target of some form of intrusive contact following the breakup of a dating or romantic relationship. Almost all of the relationships were heterosexual, although intrusive contact occurred after a few same-sex relationships. The average age of the respondents at the beginning of these relationships was about 16, showing that these were relationships often experienced by adolescents rather than college-age adults. More females than males reported being the target of intrusive contact. Nine percent of the females and 11 percent of the males had initiated intrusive contact. About one quarter of the females feared for their safety at some point during the intrusive contact, as did one of the males. About a quarter of those that had been the targets of intrusive contact said that the contact had a decidedly negative influence on their dating relationships, and about one fifth of them reported that it had a decidedly negative influence on their life in general. 5 tables, 19 references