Interest has grown in recent years in a five-factor model for the organization of personality characteristics. A brief history of the development of this model is given. It is evident that the model is very general, across variations in raters and ratees and across languages. There is also evidence that the structure of personality inventories reflects this model. Although most of the studies that have demonstrated the model have utilized either self-report inventories or have relied on ratings, there is clear evidence that both ratings and inventories are importantly related to actual behavior. A longitudinal study of children's personality traits is reported. Evidence for the five-factor model is examined, including data for the stability over time of characteristics organized in terms of the model. One trait of particular focus in this study has been Factor 3, often interpreted as Conscientiousness but here referred to as Will to Achieve because of its high correlations with formal measures of educational achievement. Studies indicate that this dimension is responsible for much of the variance in achievement left unexplained by aptitude measures.