Autoradiography is the process to detect radioactively labeled molecules (which commonly have been separated in an SDS-PAGE or agarose gel) based on their ability to develop an image on photographic or X-ray film. This procedure does not result in a linear relationship between the intensity of the signal and the amount of the radioactivity unless special steps are taken. There is now increasing use of the phosphorimagers and other modern devices to detect and quantitative radioactive molecules which have been separated in gels.