This chapter opens with a general discussion of the various types of personality, psychiatric issues, and abuse personalities negotiators are likely to encounter at a crisis incident. Using the DSM-V as the foundation, mental illness is defined and how to recognize the differences between a person with mental illness, a person with a personality disorder, and a normal person in crisis. The many unique issues encountered by negotiators in negotiating with a mentally ill person and an emotionally disturbed person are described and techniques for dealing with those issues given. The importance of understating the continuum of mental illness is presented. Specific issues related to domestic violence incidents are discussed. A detailed discussion is presented for negotiators in negotiating with persons with specific mental illnesses, including antisocial, borderline, histrionic, compulsive/perfectionistic, and narcissistic personalities; paranoid; and paranoid schizophrenics. One recent innovation in law enforcement is the use of crisis intervention trained officers. The value of working with CIT officers is presented, along with an explanation of how those officers compliment negotiators. The value and importance of utilizing a mental health professional in dealing with the mentally ill and emotionally disturbed is discussed. Negotiating with subjects who are cognitively impaired, have a developmental disorder, or are a substance abuser/dependent is discussed.