This chapter focuses on nondeviant sexual behaviors in men and women that escalate into serious consequences for the individual or others. Problematic forms of excessive sexual behavior have in recent years been given several terms, including compulsive sexual behavior, hypersexuality, excessive sexual drive, paraphilia-related disorder (PRD), nonparaphilic, sexual addiction, sexual impulsivity, and impulsive-compulsive sexual behavior. Currently, PRD can be classified as impulse control disorder, not otherwise specified or as sexual disorder, not otherwise specified. Problematic forms of excessive sexual behavior may be classified in the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) in a new category of disorders named behavioral and substance addictions. Sexual obsessive thoughts are common in obsessive-compulsive disorder (OCD). The Multiphasic Sex Inventory (MSI) is primarily intended to be used in assessing sexual offenders to develop treatment plans and to assess progress during treatment.