An enzyme-linked immunosorbent assay (ELISA) for progesterone measurement in serum or plasma samples using penicillinase as label enzyme is reported. A C3 and C11 derivatives of progesterone were prepared and conjugated to bovin serum albumin (BSA). Polyclonal antibody against these two immunogens were prepared in New Zealand white rabbits. Purified Ig fractions of antibodies were immobilized o...