Objective/Context: In this research we analyze the change in heterosexual masculinities in Argentina and Mexico during the second half of the twentieth century with a special focus on working class men who, while playing the insertive role in sex with maricas, jotas and gays, still considered themselves and were perceived by their peers to be straight. The evidence shows that, although sex between maricas and young heterosexual men occurred frequently, it was not stigmatized by straight peers, nor did it erode the perceived heterosexuality of these young men in any way. Methodology: In order to explore the representation of sexual activities from the point of view of those involved we conducted in-depth interviews and used a wide range of historical evidence, such as autobiographical literature, ethnographies, and judicial records, materials that have not previously been analyzed together. In addition to discussing self-representations, this paper also analyzes the ways in which scholars and activists from the time period perceived sex between men and the associated identitites. Originality: This paper rests on a comparative approach that helps to reconstruct regional historic and social processes in the midterm. This is the first paper that studies the problem from these straight young men's point of view, based on a novel and diverse corpus. Conclusions: In opposition to the prevailing analysis, this paper develops a counter-intuitive hypothesis: given that sex between men did not deprive heterosexual men of their identity and, instead, it constituted a way of reaffirming their masculinity, these sexual activities between men cannot be categorized as homosexual. On the contrary, the very performance of same-sex sexuality served to shape heterosexuality. [ABSTRACT FROM AUTHOR]