The paper reports the status of the U.S. Environmental Protection Agency's (EPA's) bioresponse-based testing program. Chambers for creating controlled emissions from sources are basically the same as have been used for traditional studies of emission rates and chemical compositions. Studies of human subject responses to known odorous or sensory irritant chemicals using nose-only, eye-only, facial, and whole-body exposures are providing baseline data against which animal and in vitro results will be validated. The animal and in vitro methods being investigated measure changes in respiratory patterns and chemosensory evoked potentials.