The criminal behaviors of harassment and menacing are difficult to control, and of increasing concern to the general public and local law enforcement officials. In 1992, the New York State Legislature modified the Penal Law, responding to public fears and concerns that stalking behavior may become violent. Some persons charged with these types of offenses are suffering from psychiatric disorders. Among these disorders are those classified as Delusional Disorders. According to both DSM-III-R (1987-1993) and DSM-IV (1994), there are five specific types of Delusional Disorder: erotomanic, grandiose, jealous, persecutory and somatic. This type of disorder tends to be chronic. Forty eight cases of persons charged with harassment and menacing in the New York County Criminal and Supreme Court and referred for evaluation to the Forensic Psychiatry Clinic between January 1987 and January 1994 are reviewed. When cases of erotomania and other affectionate/amorous complaints were compared with persecutory/angry forms of harassing behavior, there was a great deal of similarity. When all harassers were compared to the Clinic population as a whole, major differences in ethnicity, age, educational level and sex were noted. Findings are presented regarding incidence, other demographic data, recidivism, violence and clinical diagnosis. The researchers conclude that erotomania does exist, however, there are other psychiatric disorders which can also be diagnosed in individuals accused of harassing and menacing behavior. From the point of view of the victim and the criminal justice system, the similarities in behavior patterns are more important than the different diagnoses.