The main objective of this study is to understand the development of homosexuality in Thai and American movies by using a comparative content analysis of the selected films from 1970 to 1999. 16 American and 8 Thai movies that share some parts of homosexual behavior of heroes, supporters, or minors are selected as sample for study. For the analytical purpose the 24 movies are divided into 3 periods. The study shows the different parts of development of the American and Thai movies. For the American side, the presentation of homosexuality in the movies has been continuously progressive. We have seen the increasing number of homosexual movies as the time goes by and the homosexual behavior has shown among the roles of heroes, supporters, and minors. Those roles are various, complicated and in fact look like those of normal men and women. It is obvious that the homosexual development of the American movies have been influenced by the homosexual movements in American society in each period. The presentation of homosexuality in Thai movies is quite different. Here the middle period became the peak for homosexual movie development. This can be seen from the number of movies and homosexual roles spreading around the heroes, supporters, and minors. In addition, the movie role development during this time compared with the first and present periods was various, complicated and acting like normal men and women. According to the study Thai movies have been influenced by the factors of a need for new and challenging ideas in the movies and of individual homosexual struggles to survive. Lastly the result of the research shows that American movies, compared to Thai, could reflect more the homosexuality existence in the society and could influence Thai audiences more effectively.