The article introduces a method called Arbitrarily Primed PCR (AP-PCR) for generating simple and reproducible fingerprints of complex genomes using single arbitrarily chosen primers and the polymerase chain reaction (PCR). The method involves two cycles of low stringency amplification followed by PCR at higher stringency. The authors demonstrate that strains can be distinguished by comparing polymorphisms in genomic fingerprints. The method is applied to twenty-four strains from five species of *Staphylococcus*, eleven strains of *Streptococcus pyogenes*, and three varieties of *Oryza sativa* (rice). The results show that AP-PCR can produce species- and strain-specific fingerprints, with the number, reproducibility, and intensity of bands depending on parameters such as template concentration, primer annealing temperature, and primer sequence. The method is also shown to be useful for detecting polymorphisms and constructing phylogenetic trees. The authors discuss the potential applications of AP-PCR in epidemiology, population genetics, and breeding programs.The article introduces a method called Arbitrarily Primed PCR (AP-PCR) for generating simple and reproducible fingerprints of complex genomes using single arbitrarily chosen primers and the polymerase chain reaction (PCR). The method involves two cycles of low stringency amplification followed by PCR at higher stringency. The authors demonstrate that strains can be distinguished by comparing polymorphisms in genomic fingerprints. The method is applied to twenty-four strains from five species of *Staphylococcus*, eleven strains of *Streptococcus pyogenes*, and three varieties of *Oryza sativa* (rice). The results show that AP-PCR can produce species- and strain-specific fingerprints, with the number, reproducibility, and intensity of bands depending on parameters such as template concentration, primer annealing temperature, and primer sequence. The method is also shown to be useful for detecting polymorphisms and constructing phylogenetic trees. The authors discuss the potential applications of AP-PCR in epidemiology, population genetics, and breeding programs.