With therapeutic, diagnostic, and incidental exposure to electromagnetic radiation (EMR) growing at a rapid pace, with the likelihood of increased environmental impact of EMR from long-range power transmission and from communications devices, it is imperative that a firm body of knowledge be established regarding the basic biological consequences of being immersed in such an environment.  The dual focus of this project will be (1) on the influence of low-level by prolonged exposure to EMR on the performance of complex operant tasks and (2) the physical and behavioral development of animals subsequent to their being exposed to EMR prenatally or as neonates.  Using a unique facility for accurate, dose matched and simultaneous exposure of many subject to preselected levels of microwave radiation (MWR) at 2450 Mhz, adult rats, pregnant rats and rat pups will be exposed at dose rates of from 0.5 to 6.0 mW/g. The irradiation facility will consist of 32 combination waveguide exposure and behavioral chambers, so that appropriate operant trials can be run on the adult animals concurrent with MWR exposure.  Each experimental group will be paired with a control group that is subject to identical conditions except for the absence of MWR.  MWR dose rates will be specified in terms of whole body specific absorbed-dose rates, and in terms of the regional distribution of that does, as determined by time-temperature measurements in separate calibration studies.  The behavioral measures to be studied include the rate of acquisition and skill at complex operant tasks, development of simple reflex/motor skills, and levels of alertness and reactivity as function of age and exposure history.  The goals of these studies include a definition of the risks inherent in long term exposure to low level MWR as an adult, in short duration exposure while the organism is still in a developmental stage, and thereby providing quantitative support for the future development of safety standards regarding exposure to electromagnetic radiation that take into account the possibilities of adult, prenatal and/or postnatal exposure.