There is increasing evidence in SSA that once infected with HIV men are disadvantaged compared to women in terms of uptake of treatment. In Uganda fewer men are on treatment, they tend to initiate treatment later, are difficult to retain on treatment and have a higher mortality while on treatment. This article discusses how men's response to HIV infection relates to their masculinity. We conducted participant observation and in-depth interviews with 26 men from a rural setting in eastern Uganda, in 2009-2010. They comprised men receiving HIV treatment, who had dropped treatment or did not seek it despite testing HIV positive, who had not tested but suspected infection, and those with other symptoms unrelated to HIV. Thematic analysis identified recurrent themes and variations across the data. Men drew from a range of norms to fulfil the social and individual expectations of being sufficiently masculine. The study argues that there are essentially two forms of masculinity in Mam-Kiror, one based on reputation and the other on respectability, with some ideals shared by both. Respectability was endorsed by 'the wider society', while reputation was endorsed almost entirely by men. Men's treatment seeking behaviours corresponded with different masculine ideologies. Family and societal expectations to be a family provider and respectable role model encouraged treatment, to regain and maintain health. However, reputational concern with strength and the capacity for hard physical work, income generation and sexual achievement discouraged uptake of HIV testing and treatment since it meant acknowledging weakness and an 'HIV patient' identity. Men's 'dividuality' allowed them to express different masculinities in different social contexts. We conclude that characteristics associated with respectable masculinity tend to encourage men's uptake of HIV treatment while those associated with reputational masculinity tend to undermine it.