In this study, it is aimed to provide an up-to-date overview of different types and application areas of polymerase chain reaction (PCR) developed with technological advances. PCR has accelerated scientific studies with its use in medical research and molecular biology. PCR based methods are used in many fields such as diagnosis of infectious diseases, microorganism typing, gene expression analysis, epidemiology and taxonomy fields, oncological studies, DNA cloning, analysis of point mutations, insertion of transposon elements, polymorphism studies, population typing, phylogenetic analysis, drug level analysis, and autoantibody detection. Multiplex PCR is used for simultaneous amplification of multiple targets using multiple primer pairs, consensus PCR is used for amplification of common (conserved) gene regions of genetically related microorganisms, rep-PCR is used for amplification of repetitive fingerprint DNA sequences in microbial genomes, nested PCR is used to reduce non-specific primer binding and increase sensitivity, hot start PCR is used to reduce the presence of non-specific products and primer dimers, anchored PCR is used to enable amplification of unknown gene regions using non-specific anchor primers, ligation mediated and homopolymer PCR is used for amplification of a DNA segment with a single known primer binding site, touch-down and touch-up PCR is used to prevent mismatches by regulating annealing temperature, autosticky PCR is used for amplification of DNA fragments for gene cloning using abasic primers, methylation specific PCR is used to determine the methylation patterns of cytosine residues, inverse PCR is used for sequence analysis of unknown flanking DNA regions, asymmetric PCR is used to synthesize single-stranded DNA using primers of different concentrations, in-situ PCR is used to visualize intracellular amplification in tissue sections, RAPD is used for amplifying random DNA segments using random primers and for population analysis, immuno-PCR is used for detection of low concentration amplicons by combining ELISA and PCR methods, real-time PCR is used for quantitation and monitoring of amplification with real time fluorescent signals, digital PCR is used for absolute quantitative amplification, long-range PCR for amplification of long target DNA regions, and reverse transcription PCR is used to provide amplification by synthesizing cDNA from RNA with reverse transcriptase enzyme. PCR modifications have developed rapidly throughout history. Having knowledge about these modifications will be an eye-opener for new methods to be discovered with technological developments, will contribute to selection of appropriate methods, and will increase the sensitivity and specificity of the reactions.