There's a new study by the National Institute of Environmental Health Sciences examining possible links between cellphone use and cancer. As has been true of earlier studies, it offers no definite conclusion.
The study subjected rats to the same kind of non-ionizing radiation a cellphone produces. In the study, half the rats were exposed to the radiation, half not. Of the male rats exposed to radiation, about 2 to 3 percent developed brain cancer. Of the rats not exposed, none developed brain cancer. On the surface, that seems fairly convincing that cellphone radiation can cause cancer.