Five basic personality dimensions are Extraversion, Agreeableness, Conscientiousness, Neuroticism, and Openness to Experience. Model structures traits hierarchically. Natural language adjectives support the model. Personality questionnaires confirm the model. Model is comprehensive. Model applies across observers. Model applies across cultures. Research summarizes model history. Research details supporting evidence. Article discusses factor nature. Article outlines theorizing agenda on factor origins. Article outlines theorizing agenda on factor operation. Model aids individual assessment. Model elucidates personality psychology topics.