In a response to comments by P. T. Costa, Jr., and R. R. McCrae on the current authors' original article, the authors show that Costa and McCrae's writings on personality suggest a belief in immutability of personality traits. The authors agree with Costa and McCrae that new personality trait models that provide an accurate lower order structure of personality traits are needed and explain why the Revised NEO Personality Inventory is not the correct model for that purpose. The authors provide direct evidence refuting the hypothesis that personality traits change only because of biologically based intrinsic maturation. The authors present arguments supporting the contention that meta-analyses should be preferred to single longitudinal studies when drawing inferences about general patterns of personality development. Finally, the authors point out why the differences between their position and Costa and McCrae's are important.