The authors applied I-States as Objects Analysis (ISOA), a recently proposed person-oriented analytic approach, to the study of temperament development in 921 Norwegian children from a population-based sample. A 5-profile classification based on cluster analysis of standardized mother reports of activity, sociability, emotionality, and shyness at ages 18 months, 30 months, 4-5 years, and 8-9 years was interpretable and highly replicable. The prevalence of temperament profiles changed markedly with age, and individual stability in temperament profiles was significant. Specific typical and atypical developmental sequences of profiles were identified. Selective patterns of concurrent group differences in externalizing and internalizing problems by temperament profiles were remarkably similar across ages. The findings to some degree support the notion that individual temperament-variable values take on meaning in relation to the whole individual configuration and indicate some lawfulness in temperament changes over time. Future person-oriented studies of temperament development should replicate the current results using multiple data sources, rigorous tests of gender differences, and latent group modeling.