transgender identities pose major challenges to the dominant psychosocial perspective on sex and gender. this paper discusses some of the ways in which transgender identities can challenge the dominant sex/gender logic pervading psy science. in particular, the paper focuses on how these identities allow us to rethink two well-established dichotomies concerning the concept of gender: the sex-gender distinction and the man-woman binary. by using illustrative cases, the analysis draws upon testimonial evidences and material collected from individuals and trans-gender activists from previous research. finally, we present a discussion about the possible implications of the reformulation of these dichotomies for a psychosocial perspective on gender and identity.