Introduction: The purpose of this study was to determine whether ultrasonography allows precise assessment of the course and relations of the infrapatellar branch of the saphenous nerve. Methods: This work, initially undertaken in 5 cadavers, was followed by high-resolution ultrasonographic study in 10 healthy volunteers. The location and relations of the infrapatellar branch of the saphenous nerve to the adjacent anatomical structures were analyzed. The course of the nerve was classified according to its relation to the sartorius muscle as posterior or penetrating. Results: The infrapatellar branch of the saphenous nerve could be identified consistently along the majority of its course by ultrasonography. Useful landmarks for the detection of the nerve could be defined. Some anatomical variations were noted. Conclusions: The infrapatellar branch of the saphenous nerve can be depicted by ultrasonography. Precise mapping of its anatomical course may have significant clinical applications. Muscle Nerve 44: 50-54, 2011