Personality disorders are enduring patterns of thinking, feeling and behaving that deviate from cultural norms and lead to distress or impairment. They are classified into three clusters - A (odd/eccentric), B (dramatic/erratic) and C (anxious/fearful). Specific disorders discussed include paranoid, schizoid and schizotypal PD from cluster A, antisocial, borderline, histrionic and narcissistic PD from cluster B, and avoidant, dependent and obsessive-compulsive PD from cluster C. Each disorder is defined by a set of diagnostic criteria and statistics on prevalence, etiology, course and treatment options are provided.