Currently postulated mechanisms of perineural invasion (PNI) include interaction between tumor cells and nerves. Neural cell adhesion molecule (N-CAM), one of the well-known members of the immunoglobulin super-family of adhesion molecules, was implicated in PNI and metastasis in various types of cancer. Tissue microarray technology was used to build 2 sets of tissue array (with versus without PNI) from 50 prostate cancers (PCa). The slides were stained immunohistochemically, and the results were evaluated semiquantitatively using a 0 to 3+ scoring system. N-CAM staining was observed in all nerves with variable intensity. N-CAM expression was upregulated in 73% (31 of 42) of the nerves with PNI compared with nerves without PNI (P >.001). The results suggested that N-CAM is probably involved in PNI in PCa. It is conceivable that cancer cells, through a yet-to-be-established paracrine loop, signal the nerve to increase N-CAM production and increase adhesion. N-CAM upregulation in nerves may also facilitate cancer cells to migrate toward nerves and promote the process of perineural spread through increased survival using the nuclear factor kappa B pathway.