Temperament in young infants is assumed to constitute the building stones of later personality. Our approach to this research area includes development of instruments for description of early differences in behavior, and a focus on research questions concerning the importance of early individuality for both child development and parenting. We have studied infant and preschool temperament in combination with attachment and other environmental aspects as antecedents to middle childhood dimensions in the Five Factor Model of personality (extraversion, agreeableness, conscientiousness, neuroticism, and openness). We have also found that infant temperament, mainly irritability and irregularity, seems to play a role for maternal interactive behaviors and for experiences of parenting stress, parenting role satisfaction and perceived control over child development. Connections from early temperament to later child problems such as externalizing and feeding problems as well as from personality dimensions in school age to concurrent behavioral adjustment have been explored.