Stable behavior style in day nursery children and in their parents is examined by means of questionnaires. The multi-dimensional structure of temperament is demonstrated, maternal and paternal estimates are compared and social-economical position of a family and its influence on children's temperament evaluated. It is shown that temperament in young children can be conditioned by psycho-physiological characteristics such as inhibition system. Environmental factors play their role in temperament formation too. Temperament is an important parameter in the formation of life style.