In the diagnosis and treatment of behavioural disorders in multi-cat households, it is often assumed that a dominance hierarchy exists between the cats (e.g. Crowell-Davis, 2002). While such hierarchies are probably commonplace among dogs, what evidence there is to support the existence of social hierarchies in groups of domestic cats has mainly been gathered from reproductively entire animals, such as single sex laboratory colonies, and free-ranging aggregations of ferals. For example, Natoli et al. (2001) used receipt of “submissive” (defensive) behaviour to construct a weakly linear hierarchy in a group of 14 farm cats, but this did not correspond to the hierarchy derived from receipt of affiliative behaviour. We have investigated the alternative hypotheses that apparent dominance hierarchies in multi-cat households may actually be based upon territorial behaviour, or some other undetermined social system.