OBJECTIVE: This paper is the first of a 2-part review on the topic of stalking. It outlines the behaviours involved, epidemiology, motivation of offenders, and mental health consequences for the victim. METHOD: Computerized literature searches were used to identify relevant papers from psychiatric and legal journals. Publications by victims' and women's organizations provided additional information. RESULTS: Up to 1 in 20 women will be stalked during her lifetime. The majority of victims are female, while the offenders are usually male. Stalking behaviours range from surveillance to threatening aggressive or violent acts. The majority of stalking relates to failed intimate relationships. Stalkers may also suffer from erotomania or obsessional love with a primary psychiatric diagnosis. Victims may experience anxiety, depression, guilt, helplessness, and symptoms of posttraumatic stress disorder (PTSD). CONCLUSION: Stalking is a serious offence perpetrated by disturbed offenders. It can cause major mental health consequences, which are often poorly understood by society.