Silver staining of polyacrylamide gels was introduced in 1979 by Switzer et al. (1) and rapidly gained popularity owing to its high sensitivity, ca. 100 times higher than staining with Coomassie blue. However, the first silver-staining protocols were not trouble-free. High backgrounds and silver mirrors were frequently experienced, with a subsequent decrease in sensitivity and reproducibility. This led many authors to suggest improved protocols, so that more than 100 different silver-staining protocols for proteins in polyacrylamide gels can be found in the literature. However, all of them are based on the same principle (see refs. 2 and 3 for details) and comprise more or less four major steps.