近期已有司法判決認定戶政事務所不得以跨性別者未檢附變性手術證明文件，而拒絕辦理性別變更之申請登記。倘日後性別變更登記並非以施作變性手術為必要，則可預期選擇變更法律上性別，以符合個人性別認同之人數將日漸增多。又司法院釋字第七四八號解釋施行法施行後，相同性別之二人得辦理同性婚姻登記，即可能發生「異性婚後，因一方變性使二人成為同性」或「同性婚後，因一方變性使二人成為異性」等情形，且因民法及前開釋字第七四八號解釋施行法，對於離婚、收養等要件容有差異，故一方於婚後變性後應適用何法規，恐會對婚姻之法律效力產生影響，因此本文認有討論及分析之必要。

In recent years, there has been a judicial decision which determined that the Household Administration Bureau should not reject the applications for gender registrations from transgenders without certificates of sex reassignment surgery. Due to the promotion of gender equality and medical advancement, if such certificates of transsexual operations are not required, it is expected that there will be more people who want to change their legal genders to fit individual gender identity. According to the enforcement of Act for Implementation of JY Interpretation No 748, two same-sex persons could apply for marriage registrations at the Household Administration Bureau. In that case, if someone changes his/her gender after different-sex marriage or same-sex marriage, due to that the requirements of divorce, adoption, etc. are different in Civil Law and by Act for Implementation of JY Interpretation No 748, which law is to apply may influence the legal validity of the marriage. This is the reason why it is essential to discuss and analyze these issues in this article.