We need methods to measure friendship among very young children to study the beginnings of friendship and the impact of experiences with friendship for later development. This article presents an overview of methods for measuring very young children's friendships. A behavioural sociometric method was constructed to study degrees of friendship among children in daycare centres. Friendship indications of earlier studies were verified. Data were collected by behavioural observations of 674 dyads during their free play in daycare groups. Explorative factor analysis showed a strong significant relationship among playing together, prosocial behaviour, initiatives and imitation, which could be explained by friendship. This association with friendship was not found for quarrels, rejections and proximity during snack and lunch times. Our study showed that the number of children who have one or more friends in daycare depends on the behavioural criteria used in several studies.