The stability of individual differences in personality traits is typically examined at the group level with test-retest correlations across two assessments. For 684 subjects (age range 17-76) we computed individual coefficients from three sequential assessments to evaluate intra-individual (i.e., within-person) change in stability over time. For both trait and profile (ipsative) stability, results indicate that intra-individual stability increases up to age 30 and then plateaus. Neither demographic variables (sex, ethnicity, education, and secular trends), nor the standing on the five major dimensions of personality, were predictors of change in trait stability. Contrary to results from studies of adolescents, personality "maturity" was unrelated to personality stability in adulthood. These findings support the notion that personality stability plateaus early in adulthood.