臺灣既有同性戀量化研究相當稀少，以致於在討論同性戀人權或同性婚姻相關議題時，缺乏足夠的研究報告與數據供政府或民眾參考。中央研究院社會學研究所「臺灣青少年成長歷程研究」，於 2011年進行青少年邁入成人初期的性傾向調查，是研究多元性傾向議題的珍貴素材，唯截至目前為止鮮少有相關命題使用此一資料進行研究。本文研究目的旨在利用該資料，精確且全面地從慾望、行為與認同三個面向，測量與估計臺灣北部成人初期的同性戀者與非異性戀者的百分比。分析結果顯示，臺灣北部 24至 29歲年輕人中，約有 2.85％的男同性戀者與5.21％的女同性戀者，且不論就慾望、行為或認同面向觀察，女性同性戀傾向的人口百分比皆較男性多，與西方研究結果相似。此外，約有8.86％的男非異性戀者與27.65％的女非異性戀者，女非異性戀者百分比多達四分之一強；但其中有將近 8％的女性是僅擁有同╱雙性慾望，有同╱雙性交往或同╱雙性行為的情況較少，顯示臺灣年輕女性性傾向的多元面貌。

In Taiwan there are a limited number of quantitative studies of homosexuality and homosexual practices in the research literature. The scarcity of such research has led to confusion in the public discourse on homosexuality and civil right issues regarding same-sex marriage legislation in recent years. In 2011, the Taiwan Youth Project conducted by the Institute of Sociology at Academia Sinica deployed a self-administered questionnaire to examine sexual inclination and practices from a cohort of 24-to 29-year-old adults in northern Taiwan. The purpose of this study is to utilize the 2011 Taiwan Youth Project data to estimate the proportion of homosexuals and non-heterosexuals among the respondents, based on three dimensions of sexual orientation, namely desire, behavior, and identity. The research findings show that there are approximately 2.85 percent male homosexuals and 5.21 percent female homosexuals among the population of 24-to 29-year-old adults in northern Taiwan. Our results resonate with existing studies showing that females in early adulthood have a stronger inclination toward homosexuality in terms of these three dimensions of sexuality. In addition, there are approximately 8.86 percent male non-heterosexuals and 27.65 percent female non-heterosexuals among the population of 24-to 29-year-old adults in northern Taiwan. However, although 8 percent of female respondents expressed bisexual desire, only a few are involved in actual bisexual relationships or behavior. Our results underscored the diversity of females’ sexual orientation in northern Taiwan, similar to findings of many other studies in Western societies.