Exploratory and confirmatory factor analyses using different personality measures in three samples confirmed the existence of general factor of personality (The Big One) within the five-factor model. The Big One is characterized by high versus low Emotional Stability, Conscientiousness, Agreeableness, Extraversion, and Openness, and by high versus low higher-order factors of personality, Stability, and Plasticity. A comprehensive theoretical model of personality structure was therefore proposed with the Big One at the highest level of the hierarchy. The Big One was interpreted as a basic personality disposition that integrates the most general non-cognitive dimensions of personality. It is associated with social desirability, emotionality, motivation, well-being, satisfaction with life, and self-esteem. It also may have deep biological roots, evolutionary, genetic, and neurophysiological.