Abstract: This research merges the enzyme-multiplied assay technique (EMAT) with photometry and amperometry to produce a detection system capable of screening for hormone-mimicking chemicals and benzodiazepine drugs. EMAT relies on a reporter enzyme, β-galactosidase (β-gal), which has a target ligand covalently coupled to its surface, for signal generation. When ligand-specific binding protein (antibody or receptor) binds to the enzyme-conjugated ligand, the enzyme's active site is blocked or frozen rendering the enzyme inactive. The addition of analyte, as in the form of free ligand, competes with the enzyme-ligand conjugate for antibody or receptor binding. The association of the binding protein to the free analyte in solution relieves the active site inhibition and allows substrate to be processed by the enzyme; thus, the enzyme's activity is now de-repressed. Thus, the presence of free analyte is reported by the enzyme, which 'multiplies' the ligand-antibody dissociation event by turning its substrate over repeatedly. The β-gal substrate analog, o-nitrophenyl β-D-galactopyranoside, yields the visibly colored, o-nitrophenyl product upon hydrolysis; whereas the substrate, p-aminophenyl β-D-galactopyranoside gives rise to an electrooxidizable product, p-aminophenol. These β-gal substrates make possible the demonstration of both photometric and electrochemical signal transduction schemes for β-gal-based EMAT. EMAT has been demonstrated for estimating human estrogen receptor affinity to endocrine disrupting chemicals as well as determination of relative central benzodiazepine receptor affinity to the benzodiazepine class of drugs. The construction of an amperometric biosensor probe shows the potential for developing field-deployable EMAT sensors.