This chapter discusses personality disorders (PDs) as these disorders are frequently encountered in clinical settings and have impacts on morbidity and mortality and significant treatment implications. In this chapter, we discuss the history of personality diagnoses and the importance of personality diagnoses, recognizing patients with personality disorders, and review the most common and most researched disorders including: antisocial, avoidant, borderline, narcissistic, obsessive compulsive, and schizotypal personality disorders. This chapter concludes with a discussion of the psychopharmacological and psychotherapeutic management of these disorders.