The aim of the present study was to obtain some insight in how children structure and organize their knowledge about other people. Ten short descriptions of social situations (i.e., interactions) illustrated by pictures were presented to 48 children from four different age groups (mean ages 5.4, 6.7, 8.6, and 10.7 years). The situations were accompanied by questions pertaining to the story characters as individuals, their thoughts, their (re)actions, and the immediate causes of their behaviour. The results showed that the knowledge about each concept is highly age related. Partial correlations indicated that concepts about individuals and concepts about the immediate causes of behaviour are related to concepts about how people will (re)act in particular situations. In addition, the concepts about individuals are related to concepts about the thoughts and concepts about the immediate causes of behaviour. It appeared that the better the children seem to know other people the less certain they were in regard to their inferences about others.