Cyberstalking involves the use of the Internet or other electronic communication to stalk another person. Already common, it is likely to become more common as the use of the Internet continues to grow. The characteristics of online stalkers and their victims have some differences from those of the offline stalker. Mullen, Pathé, Purcell, and Stuart’s (1999) classification may apply to cyberstalkers except for the apparently common phenomenon of child luring that may be a new category. The methods of cyberstalking, as described in this chapter, are particularly ingenious. We know little about the effect on victims, but postulate that it is similar to offline stalking. We make some suggestions that may prevent cyberstalking, as well as offer some steps to bear in mind once cyberstalking occurs. The proliferation of personal computers with Internet access in the last decade has raised concerns about a new phenomenon known as cyberstalking. The Internet can be used to annoy and harass large numbers of victims in a generic manner by disseminating computer viruses, Internet scams, and “spamming” people with unsolicited e-mail. In 1999 Janet Reno, the attorney general of the United States, defined cyberstalking as the use of the Internet, e-mail, or other electronic communications devices to stalk another person (Reno, 1999). Barak (2005) looked at the issue of sexual harassment on the Internet. He characterizes cyberstalking as one type of sexual coercion. He notes that online behavior is characterized by disinhibition, openness, venture, and bravado—an atmosphere characterized by typical masculine attitudes. He argues that the lack of legal boundaries or enforcement vehicles encourage people to do what they would not have done in offline situations. He notes the near impossibility of implementation of legal procedures on a large scale. In this chapter we will discuss what is known about the prevalence of this phenomenon, the types of cyberstalking, and what is known about the perpetrators. In addition, we will generate some hypotheses about the comparison between online and offline stalkers. We will also discuss the effects on victims and current thoughts and resources for dealing with cyberstalking.