In 1961, George Maciunas first met the artists and composers whom he would organize into the neo-avant-garde movement known as Fluxus. That same year, he acquired a persistent cough that was later diagnosed as asthma. Drawing from disability-studies scholars including Alison Kafer, Rosemarie Garland-Thomson, Jasbir K. Puar, and Ellen Samuels, “Prescribed Performances” considers the historical dimensions of this coincidence. Maciunas belonged to a new class of medical subject, the patient of chronic illness who depended on postwar medical innovations (such as steroids) and integrated a regime of self-management into their everyday life. To chart where and how the subject presented in neo-avant-garde performance intersected with the one produced by an emerging biopolitical apparatus for regulating public health, this article turns to the first Fluxus concerts, held in Europe in 1962–63, and then moves forward into the 1970s, asking how event scores, multiples, happenings, and body art were all inflected by their authors' experiences of debility, gender, sexuality, race, nationality, and precarity. Maciunas's Solo for Sick Man (1962), FluxClinic (1966), One Year (1973–74), Hospital Event (1975–76), and Flux Wedding (1978) will be discussed in relation to works by George Brecht, John Cage, Hi Red Center, Allan Kaprow, Alison Knowles, Shigeko Kubota, Charlotte Moorman, Nam June Paik, and La Monte Young.