I will start by briefly explaining where I am coming from and the type of research I've done. I'll then move on to look at the way in which certain types of trans and intersex identity challenge gender and sexual orientation binaries. Then I'll outline and evaluate some of the different strands of gender theory, (leaving out queer theory here as I don't have enough time to cover it) before finishing by outlining three alternative approaches to understanding gender diversity. My theory work includes people who do not identify as trans, as well as those who do. I'd like to emphasise that I realise that many trans and intersex people identify as completely male or female, so that discussing gender as a broader spectrum is not relevant to them personally. And, one of the difficulties with doing theory work is that it is impossible to avoid generalising to an extent - I hope that I have not ignored the diversity within our communities.