Although many studies of conflict behaviour in mice have been made, the activities associated with the behaviour are ill defined. The present study is directed to an elucidation and understanding of the behavioural concomitances of conflict behaviour. Isolated mature male C57BL/10J mice, an inbred strain of the house mouse, Mus musculus, served as subjects. They were divided into twelve categories of four mice each and tested by the round robin method. A single food pellet was introduced in six of the twelve categories at the time of testing. The amount of time spent in an activity or the number of occurrences of a behavioural pattern were recorded. The dominant mice spent significantly more time in social grooming, social sniffing, genital sniffing and food control than did the subordinate mice. Humping and tail lashing also were exhibited significantly more by the dominants. Significantly more tail lashing occurred in pair contacts when fighting, usually accompanied by attacks and chases, took place than when only attacks and chases occurred. Correlations between latency and time spent in conflict behavior and in social sniffing were significant. It is concluded that tail lashing appears to be related to conflict behaviour and probably serves as a threat to other animals. Humping is probably related to the mincing and excitatory running reported by other workers. Social grooming appears to be related to conflict behaviour in some cases, while in other instances it appears to be a more amicable type of behaviour. Several characteristics are associated with dominance in mice. Dominant animals engage in a greater amount of tail lashing, humping, social grooming, social sniffing, genital sniffing, and control of a food pellet than do subordinate mice.