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This paper summarizes the weight of scientific evidence on whether or not exposure of laboratory animals to radiofrequency (RF) energy a) causes or promotes tumor development and b) affects the integrity of the blood-brain barrier (BBB). Forty-four studies of tumorigenesis were identified. In addition to the studies of spontaneous tumorigenesis in animals exposed to RF energy alone, 21 of the 44 studies investigated tumor promotion in animals exposed to RF energy in combination with chemicals [e.g., ethylnitrosurea (ENU) and 7,12-dimethylbenz[a]anthracene (DMBA)] and physical agents (e.g., x-rays and ultraviolet radiation) known to cause cancer. Evaluation of the results in all 44 studies on tumorigenesis showed no adverse effect of RF exposure up to two years in duration at dose rates up to 4 W/kg (10 times greater than the occupational safety limit) on carcinogenic processes (initiation, promotion and co-promotion). Other information in these studies on survival and body mass provides supporting evidence for the conclusion that RF exposure does not affect tumor development because a) 26 of 27 studies since 1983 reported no significant change on survival and b) all 27 studies reporting body mass observed no significant change in this health indicator. The weight of evidence of 44 animal tumorigenic studies supports the conclusion that RF exposure within current internationally accepted limits, when given alone or in combination with carcinogens, is unlikely to affect tumor development in human beings. Furthermore, the results showing a lack of RF effects on tumorigenesis, survival and body mass in live animals offer a strong challenge to studies reporting potential genotoxic and other health effects based on research with cells in culture and other biological samples exposed in vitro to RF energy. Another area of research has focused on whether or not RF exposure could affect the integrity of the blood-brain barrier (BBB) that protects the brain from potentially to- - xic molecules in the blood. A number of laboratories have confirmed that the permeability of the BBB can be affected if the temperature of the brain is increased significantly. The effect is a temperature effect because it does not matter whether the effect on the BBB was caused by exposing the animal to heated air, heated water or RF energy. Reports in the 1970s and more recent reports of changes in BBB permeability following exposure to levels of RF energy that would not significantly increase the brain temperature have failed the test of independent confirmation.