This essay deals with an aspect of polygamous marriage in Ahmed Yerima's play The Sisters. A careful reading of the play shows that Yerima is interested in depicting the 'inside' and 'outside' wives marriage system in Africa. The study shows that the concubinate is fundamental
to the play, being, as it is, the subject of dialogue. Above all, it is shown that, through theatrical techniques, Yerima seeks to approve this kind of marriage system, inasmuch as it is part of the African cultural heritage.