Gay men increasingly use non condom-based risk reduction strategies to reduce the possibility of HIV transmission. Such strategies rely on men's knowledge and communication with each other, but how they employ these strategies may depend as much on their attitudes toward risk and pleasure. We explored current beliefs about safe sex, sexual desire and risk behavior in an online survey of 2306 Australian gay men. The survey included free text components to explore men's beliefs about risk and pleasure. We conducted a principal components factor analysis on the safe sex belief items in the survey, and thematic analysis of the qualitative material was used to interrogate the concepts underpinning these beliefs. We identified two measures of safe sex beliefs: risk reduction optimism (HRRO; α = 0.703); and viral load optimism (α = 0.674). In multivariate analysis, unprotected anal intercourse with casual partners (UAIC) was associated with HRRO among non HIV-positive men only (p < 0.001), but, regardless of HIV serostatus, UAIC was associated with a belief that serosorting could be an effective risk reduction strategy and with being more sexually adventurous in general. Using the qualitative data we identified four themes in how men think about HIV: 'seeking certainty', 'regretful actions', 'nothing is safe', and 'acting on beliefs'. Each theme interacted with the safe sex beliefs measures to provide a highly contextualised understanding of men's beliefs about safe in specific circumstances. Gay men think about the risk of HIV transmission in qualitatively different ways depending on specific circumstances. While measures of belief about relative risk of HIV transmission are useful indicators of men's propensity to take risk, they oversimplify men's thinking about risk, and fail to account for the role of desire, both in influencing men's thinking about risk, and in how they balance their perception of relative risk against the pursuit of pleasure.