Specimens in natural history collections have long been considered primarily as a source of information on the morphology, anatomy or tissue structure of living organisms. Until now, most attempts to access more basic levels of complexity, such as genes or proteins have, in most cases, required resampling of fresh or living material in the wild. However, the new in vitro DNA amplification technique known as Polymerase Chain Reaction (PCR) is applicable to many museum specimens, even very old ones. This opens up a vast new field of application and will potentially give a second life to many collections. These applications are briefly presented and collections preservation is discussed in light of this new technique.