Genomic integration and mRNA transcripts of human OSM cDNA in transfected mouse melanoma cells were identified by PCR and RT-PCR methods.A sense primer for the regulatory sequence in carrier vector paired with an antisense primer for cDNA was used in integration analysis, a continuous transcription-unit was amplified with the expected size in OSM cDNA transfected cells but not in the wild type or vector control cells, reflecting a more accurate relationship between integration and expression. In transcription analysis, a sense primer for cDNA paired with an antisense primer for a sequence between the multiple cloning site and polyA signal in carrier vector was used to distinguish exogenous transcripts from endogenous gene products. This method is convenient and specific in determining exogenous gene integration and expression in transfectants.