My project traces the emergence of blood transfusion technology in modern Iran. Until the early 1970s, an informal market supplied hospitals with blood products. Forced by poverty, professional blood-sellers sold their blood to dealers who managed the market. However, altruistic donations gradually substituted blood-selling. Drawing on archival research and oral history interviews conducted in Iran, this project argues that the technology of transfusion, by appropriating the idea of kinship and intimacy and utilizing the long-lived political and religious discourse of blood, mediated and transformed not only the relationship between the state and the citizens but also the relationship among citizens whose ties to the life of strangers shaped the meaning of citizenship in modern Iran.