concrete suggestion: i generally advocate for gender as fill in the blank wherever it needs to be stated at all. here at pandys, because of the need for safety in gender-specific forums, it may be preferable to offer a choice of three checkboxes: male, female, and other, with the option to fill in a blank for "other". female- and other-identified people would not access male-only space; and male- and other-identified people would not access female-only space. general observations: as for offering "transgender" as a gender check-box... there may very well be people whose gender identity is "transgender". but for the trans people i know, while they identify as "transgender" people, that is not the *gender* that they identify as. gender identities i've heard trans people identify as include male, female, androgynous, two-spirit, genderqueer, and not gendered. i've also heard people describe their gender identity in a way that some people might not have considered a gender, e.g. butch. intersex people (those whose physical sex is mixed or ambiguous) add another dimension to the language question. respecting this rich diversity suggests not assuming that one can anticipate all possible identities; in other words, eschewing any checkbox-only approach.