What is the difference between biological sex (male, female, intersex), and gender— the range of physical, biological, mental and behavioral characteristics alleged to pertain to, and differentiate between, masculine and feminine? If gender is a social construction, that is to say, something constituted by a social world we do not choose, then is gender necessary? How and why does gender form and change in different societies, and what are the implications for those who are transgender and everyone else? This talk explores the persistence of gender and its complex relation to our bodies to advance a Marxist understanding of human liberation.