The personality disorders are grouped into three clusters based on descriptive similarities. Cluster A includes paranoid, schizoid, and schizotypal personality disorders. Individuals with these disorders often appear odd or eccentric. Cluster B includes antisocial, borderline, histri onic, and narcissistic personality disorders. Individuals with these disorders often appear dra matic, emotional, or erratic. Cluster C includes avoidant, dependent, and obsessive compulsive personality disorders. Individuals with these disorders often appear anxious or fearful. Itshould be noted that this clustering system, although useful in some research and ed ucational situations, has serious limitations and has not been consistently validated.