Highly specific antisera to triiodothyronine (T(3)) were prepared by immunization of rabbits with T(3)-bovine serum albumin conjugates. Antisera with T(3) binding capacity of up to 600 ng/ml were obtained. The ability of various thyronine derivatives to inhibit the binding of T(3-) (125)I to anti-T(3) serum was found to vary considerably. l-T(3), d-T(3) and several triiodoanalogues were potent ...