The study of effects of several parameters on silver staining of proteins has led to the development of a staining method which is simple and reliable, requires only few stable solutions, and can be applied to all gel types such as sodium dodecyl sulfate (SDS) containing polyacrylamide or isoelectric focusing gels. It can be used for ultrathin layers (0.1–0.2 mm) or thicker slab gels (up to 3 mm). With this method not only proteins but also polypeptides of molecular weights as low as 2500 are detectable with high sensitivity. Comparison of isoelectric focusing and SDS-containing gels and a simple spot test on thin gellayers show that the detection sensitivity depends not so much on the type of proteins but rather on their structure. The redox properties of the gel are important for the staining mechanism.