Substrates consisting of silver nanorod arrays with an irregular surface lattice ͑i.e., random nucleation sites͒ and with varying rod lengths were fabricated by an oblique angle vapor deposition method. These arrays were evaluated as potential surface-enhanced Raman spectroscopy ͑SERS͒ substrates using trans-1,2-bis͑4-pyridyl͒ethene as a reported molecule. SERS activity was shown to depend upon the length of the nanorods. The Ag nanorods with average lengths of 508.29± 44.86 nm, and having aspect ratios of 5.69± 1.49 exhibited the maximum SERS enhancement factors of greater than 10 8. Theoretical calculations indicate that this large SERS enhancement may be partially explained by the shape, density, and lateral arrangement of the Ag nanorod arrays.