Abstract There are many methods of inference in common use in biology that are based on population sampling, including such diverse areas as sampling organisms to determine the population structure of an ecosystem, sampling a set of DNA sequences to infer evolutionary history, sampling genetic loci to build a genetic map, sampling differentially expressed genes to find phenotypic markers, and many others. Recently developed PCR-based methods for nucleic acid fingerprinting can be used as sampling tools with general applicability in molecular biology, evolution and genetics. These methods include arbitrarily primed PCR (AP-PCR; Welsh and McClelland, 1990) and random amplified polymorphic DNA (RAPD; Williams et al., 1990) for the fingerprinting of DNA, and RNA arbitrarily primed PCR (RAP-PCR; Welsh et al., 1992a) and differential display (DD; Liang and Pardee, 1992) for the fingerprinting of RNA. Novel ways of looking at genetic control are facilitated by the high data-acquisition capabilities of the fingerprinting methods. In this article, we review some of the applications of DNA fingerprinting to the study of mutagenesis, and of RNA fingerprinting to the study of normal and abnormal signal transduction. We propose that these fingerprinting approaches may also have applications in the study of senescence and aging.