There is limited research on the impact of HIV or its treatment on men's identity construction and gender roles in sub-Saharan Africa. Based on in-depth research with 26 men in rural Uganda, this article discusses men's vulnerabilities and shifting gender relations and sense of masculinity resulting from HIV infection or enrolment on treatment in eastern Uganda. The findings suggest two broad categories of masculinity: respectable and reputational. HIV infection and illness dented masculinity as men lost authority within the domestic sphere. A weakened provider role and over-reliance on wives and children undermined masculinity as family head, and social sanctioning of their sexual activity, undermined conventional masculine identities predicted on reputation. However, treatment led to a more reflexive approach to demonstrating masculinity, increased attentiveness to health and restored hope to father children free of HIV, resuscitating respectable masculinities. The balance between eroded and restored masculinity varied between men by their treatment history, age, family composition and state of health. HIV support agencies need to pay attention to the way HIV and antiretroviral treatment (ART) influence men's perception of their masculinity and support them to overcome the anxieties about dented or eroded masculinity, while building on the positive ways in which treatment restores masculinity to support men's adherence to HIV treatment. In particular, there is a need to support men's engagement in productive activities that bring income so that men can regain their provider roles following ART and restore their respectability in both the public and the domestic sphere.