We have calculated the minimum enhancement factor for single-molecule detections from the surface-enhanced Raman scattering (SERS) data measured from well-defined silver nanorod arrays. Silver nanorods were fabricated by electrodepositing them evenly near the mouth of the pores of anodic aluminum oxide templates with a very shallow depth. The SERS intensity increased almost linearly with an increase in the concentration of the mother solution. From the data of the enhancement and the number of molecules irradiated by the laser beam at the detection limit, the minimum SERS enhancement factor for nonresonant single-molecule detections was calculated to be approximately 10(11).