Autoradiography is used to visualize and quantitate radiolabeled proteins that are resolved by 2-D protein gel electrophoresis. Proteins are commonly labeled in vivo with either ³H, ¹⁴C, ³⁵S (low-energy (β-emitters), ³²P (high-energy β-emitter), or ¹²⁵I (high-energy γ-rays). During film-based autoradiography, these emitted particles or γ-rays enter the film and cause the ejection of electrons from silver halide crystals generating local precipitates of silver atoms. In the past several years, the use of phosphor imaging has been replacing film-based autoradiography. Phosphor imaging has 10–250 times increased sensitivity compared to film-base autoradiography. While film has a dynamic range of about 300 to 1, phosphor imaging has a linear dynamic range over several orders of magnitude (1).