Publisher Summary Polymerase chain reaction (PCR) is a powerful technique in molecular biology, as it accomplishes quantitative nucleic acid analysis. With rapid advances in pharmacogenetics and pharmacogenomics, PCR is playing an important role in medical diagnosis. PCR is the most frequently used tool for molecular genetic analysis. Evidence indicates that PCR-based testing is a useful adjunct for the diagnosis of malignant tumors. This method can also detect chromosomal translocations in tissue samples. Besides the many advantages, there are many limitations of the method. There are difficulties in discerning if a PCR product is biologically relevant based on its size alone. Therefore, the PCR product should be sequenced, facilitating the identification of the PCR products.