Bering a sperm donor is often framed as an easy job. Men only have to masturbate into acup and receive money in return, at least that’s what many people assume. Turning to theexperiences of Danish sperm donors, I argue that this conception of sperm donation asselfish pleasure and commodified practice offers only a limited understanding of what itmeans to provide semen samples for reproductive donation. While sperm donors’affective investments are most of the time taken for granted and not discussed, they areactually important to consider analytically if biosocial subjectivation—the persistentinvocation of the subject in terms of biomedical registers and biopolitical valuations—is tobe understood properly. Attending to masturbation as important in its own right, I will lookat the making of sperm donors as biosocial subjects through their affective investmentswhen producing semen samples. Based on ethnographic fieldwork at Danish spermbanks and interviews with Danish sperm donors, I will thus explore how men performatively (re)constitute their gendered and sexualised subjectivity in terms ofbiomedical registers and biopolitical valuations through masturbation.