A newly established technique of polymerase chain reaction (PCR) in situ is reported. The process involved the use of the PCR technique to amplify the target gene and to generate the radiolabelled products which was used as a probe to hybridize the target gene in situ. Ki-ras oncogene in human pancreatic carcinoma cell line (PC-2) and EBV DNA in Raji cell line were detected in situ by this technique with encouraging results. This technique has the advantages of both PCR and in situ hybridization, i.e., high sensitivity, quick amplification and precise localization. It is a rapid, simple, economical and reliable method.