We describe the development of a serum chlormadinone acetate (CMA) time-resolved fluoroimmunoassay (TR-FIA). We prepared haptens (3-CMO-chlormadinone acetate and 6- chloropregna-4, 6-dien-17, 20-diol-3-one-20-hemisuccinate), biotinylated tracers (3 ( biotinylaminopropylamido) 3-CMO-chlormadinone acetate and 3-(6-chloropregna-4, 6-dien- 17, 20-diol-3-one-20-hemisuccinylamino) 1-biotinylaminopropane), and immunogens ...