Tennessee Williams, in his play "A Streetcar Named Desire," alludes to human sexuality through the characterizations provided through the strong use of gender roles.
Stanley is characterized as the stereotypical strong male. His dominant male sexual nature is seen through his abuse of Stella and the rape of Blanche. Through both, Stanley is able to control his home. (He is able to manipulate Stella into doing as he wishes--by getting her to continually take him back. He is also able to rid himself of Blanche by raping her (which results in her complete mental breakdown).)
Blanche, on the other hand, is a very sexual creature as well. She has used sex in the past in order to survive (as seen through her history as a prostitute). Not only does her sexual past ooze into her present (through her seduction of both Stanley and Mitch), she believes herself to be far more sexually attractive than she really is (given her aging).
Essentially, Williams is stating that human sexuality can be seen as a tool of power. Both Stanley and Blanche use sex to gain the things they need (Stanley to control his home and Blanche to control her desire to stay young).