Summary of Work: Personality can be defined in terms of enduring individual differences in emotional, interpersonal,experiential, and motivational styles. The five factors of Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness provide a comprehensive taxonomy of personality traits for the description of personality in aging men and women. Collaborative studies of Candian and German samples have confirmed that the five factors are substantially heritable. The robustness of the heritability data for the factors and facets of the Five-Factor Model have encouraged investigators in LPC to attempt to define the genotypic bases of personality.Contrary to prior investigations which showed a link between the personality trait of Novelty-seeking and alleles of the D4 dopamine receptor gene (D4DR), a large-scale study completed this year found no evidence for this association. Another candidate gene relating to a different dimension of personality, Neuroticism, involves a functional polymorphism in the serotonin transporter gene (5-HTT) located on chromosome 17q12(SCL6A4 localization). Over 430 BLSA subjects were genotyped for the long and short variants of the 5-HTT polymorphism. Contrary to the original observation short variants were not higher in Neuroticism.Studies of the molecular genetic bases of personality will continue.