Cowpea trypsin inhibitor (CpTI) has been reported to have insecticidal properties against a wide range of insects. An 8-year-old insect resistant oil palm, Elaeis guineensis Jacq. variety Tenera assigned as CpTI P8 was the first transgenic oil palm tree generated by the co-transformation of pDM 402 and pCAMBIA 1301 plasmids into the immature embryos of the oil palm via particle bombardment. PCR analyses had confirmed that 100% of the tested CpTI P8 frond leaves and root tissue genomic samples showed the presence of the CpTI transgene. The partial pDM 402 expression cassette consisting of the actin promoter sequence (Act1-5'), the whole CpTI coding sequence and the Nos-3' terminator sequence was fully recovered from the CpTI P8 genome using the Act1F1/NosTR1 primer pair in subsequent PCR analysis. Moreover, Southern blotting analysis showed the presence of two hybridized fragments, 0.96 kb and 1.2 kb in size in the BamHI-digested genomic DNA and also demonstrated the stable integration of the transgene into the CpTI P8 genome. The amplification of a 425 bp RT-PCR product using the CpTI gene-specific primer pair has clearly implicated the expression of CpTI transcript. Quantitative study on the expression of CpTI gene was carried out using SYBR Green Quantitative Real Time-Polymerase Chain Rection (QRT-PCR) assay and revealed a remarkably higher expression of CpTI in the CpTI P8 tree compared to non-transformed oil palm tree. Together, these data have proven the successful gene transfer and a 7-fold increase in CpTI transcript accumulation in the leaves of CpTI P8 tree which could ultimately confer greater resistance against insect pest invasion. Interestingly, the data in present study also suggest that a simple integration pattern contributes significantly to the stability and high transgene expression in transgenic plants.