An analysis of static room-temperature-operation characteristics of a reflection-mode semiconductor multiple-quantum well etalon by a simplified two-level system formula of optical nonlinear properties and a computer simulation is presented. In the calculation for a GaAs/AlGaAs multiple-quantum-well etalon using the parameters reported in experimental measurement, it is shown that the very large excitonic optical nonlinearity is not effectively utilized for the optical bistable operation. This occurs because the effective positive-feedback mechanism which increases the etalon internal light intensity is suppressed when a hardly saturable background interband absorption tail is larger than a few thousand cm/sup -1/ at a wavelength where the large excitonic dispersive nonlinearity is observed.>