We tested 11 male Scops Owls (Otus scops) and their mates with the playback of conspecific male and female calls to determine whether their response to intruders differed according to the sex of the intruder. Eight measures of response intensity were recorded for each owl. Territorial defense appeared to be strictly cooperative with both members of a pair reacting to intruders of either sex. Males responded more strongly to male playbacks for five measures of response intensity indicating that males are more aggressive toward intruding males. Females also showed a tendency to respond stronger to female playbacks, but, overall, both sexes showed little reaction to female calls. This may provide a mechanism for polygyny in this species.