The role of sight in the dominance hierarchy of groups of eight pigs was studied by the induction of temporary blindness using opaque contact lenses or hoods which covered the face. The effect of blindness was examined in three social situations: (i) the simultaneous introduction of eight previously unacquainted, blinded pigs; (ii) groups of pigs with a known social order were blinded and (iii) a single pig within a group of known social order was blinded. The contact lenses had a minimal effect on the hierarchy formation whilst both the lenses and the hoods had no effect on the established groups. The hoods prevented hierarchy formation amongst the unacquainted pigs. It is suggested that sight alone is not necessary for hierarchy maintenance and that the hoods stopped the formation of a hierarchy by an effect other than the deprivation of sight, e.g. by covering pheromone producing areas.