Abstract.— The behaviour of unacquainted children in a two‐child play situation was compared with the behaviour of well acquainted children. Observations were made through a one‐way‐screen, mainly in accord with categories adopted from ethological child studies. Tape‐recorded speech was coded into 27 content categories. Choice of activity and content of play seemed to be determined mostly by the children's sex, whereas nonverbal acts and also some aspects of speech showed considerable differences between strangers and acquaintances. Looking at the other's face, gaze avoidance, immobility, and automanipulation were more frequent among unacquainted children, and walking was less frequent among them. Longer initial silence, smaller total verbal output, and scarcity of suggestions, orders, and negative reactions were characteristic of unacquainted children at the initial stage of meeting. Personal talk (telling about oneself and asking quesrions about the other) was more common among unacquainted children, especially girls.