French children often use a comforter in order to get appeasement. It is' a piece of tissue which they need when going to sleep. Winnicott was the first one to write about this practice ; he called it the « transitional object » but included also other phenomena under this term. A longitudinal study done with 31 children followed from birth on showed that about half of them used a comforter. Its nature, the situations, when it is used, and its frequency between 1 and 48 months are reported. Principal component analyses (for each six months or one year period) were performed on 19 children's variables (quantifying temperament, relational attitudes, and the use of a comforter) and 11 maternal variables. The results show that, during the second and third years, children who use a comforter have a better emotional balance, cry less, are more controlled, more autonomous and have a more advanced psycho-motor development. Later (fourth and fifth years), their fantasy is better developed. This practice is not correlated with a specific maternal attitude, but rather with the number of caretaker's changes. Therefore, its function seems to give a feeling of security when the environment is changing, which is frequent in our society.