The governance of assisted reproduction in Denmark through legislation regards semen as a reproductive substance and thus restricts donor semen’s reproductive potential by setting terms for its use. What is not addressed in legislation is semen’s status as an ambiguous male bodily fluid that also carries other meanings. Making semen into a governable and exchangeable substance happens instead on the practice level. Based on qualitative interviews with Danish sperm donors and ethnographic fieldwork at Danish sperm banks, this article explores how material-semiotic practices at Danish sperm banks contribute to the legitimacy of sperm donation by making donor semen into a governable reproductive substance. Inspired by the containers that are used at sperm banks, in order to handle donor semen, these practices are understood as containment practices. By managing donor semen’s lust and disgust potential, containment practices help to secure donor semen’s conversion into an exchangeable means of donor-assisted reproduction.