This paper reviews the play of children in the light of the repetition compulsion. Difficulty may be encountered in accounting for games which are reproductions of unpleasant experiences. Observation suggests that repetition in play of an unpleasant experience brings about the assimilation of an affective residue left by the experience. A specific unassimilated experience calls re-experience, passively in so far as the individual lives in accordance with the compulsive drive of id forces, and actively in so far as the repetition is an attempt, by the ego, at mastery. A passive experience is actively repeated in order to master the impression received and this activity is regarded as a measure of the masculinity in the individual's later sexual behaviour. The unfinished process of assimilation is a further drive to repetition. The function of play is thus to bring about the mastery of excitations which are painful or which have too much effect for immediate