This paper examines competing treatments—surgery and radioactive iodine (RAI, I131)—for hyperthyroidism in the context of post-colonial Cold War nuclear science in Taiwan. Although the U.S.-led Cold War Atoms for Peace project pushed for the globalization of nuclear medicine, it had to compete with the Japanese colonial legacy in Taiwan (Republic of China). This government-in-exile embraced nuclear science and ushered in RAI with staged rituals. However, this modern procedure failed to overtake the surgical approach (thyroidectomy); in fact, as late as the 1990s, well after RAI had become a standard procedure throughout the world, surgery was still the major treatment option for this common disease in Taiwan. The tension between the global and the local is rooted in infrastructure as well as the materiality, regulation and availability of the Iodine 131 isotope, and, finally, the customary practice of the surgical tradition, established since the colonial period. Thyroid diseases, especially endemic goiter, were an important issue in colonial medicine, and the study, diagnosis, and treatments of thyroid diseases were an integral part of colonial surgeons’ identity. Surgical clinics had been a fixture of institutional medicine throughout Taiwan by the mid-twentieth century. In contrast, with the exception of a few prestigious hospitals in Taipei such as the National Taiwan University Hospital, most medical institutions and clinicians were not equipped to use isotopes. The availability of I131 was also limited, as the nuclear reactor did not become active until the 1960s. The preference for surgery thus points to the significance of material and social conditions of medical practice in Taiwan, amid the backdrop of the haunting images of the atomic bombs dropped by the U.S. on nearby Japan which the Atoms for Peace Project had aimed to overcome.