The purpose of this study was to classify the spinal nerve compositions of the terminal branches of the lumbosacral plexus, providing data of their participating quantities. Twenty-five sides of the lumbosacral plexus extracted from Korean adult cadavers were used in this study. The iliohypogastric nerve was mostly arisen from L1 (88.2%, thickness L1 0.7 mm). The ilioinguinal nerve was arisen from only L1 (100%, thickness L1 0.6 mm). The genitofemoral nerve was commonly arisen from L1 and L2 (62.5%, thickness L1 0.6 mm, L2 0.7 mm). The lateral femoral cutaneous nerve was classified into 4 types, and the most common type was that L2 and L3 composed this nerve (56.0%, thickness L2 0.8 mm, L3 0.4 mm). The femoral nerve was classified into 2 types, and it was usually composed of L2, L3 and L4 (88.0%, thickness L2 1.4 mm, L3 2.7 mm, L4 2.3 mm). The obturator nerve was arisen from L2, L3 and L4 in all cases (100%, thickness L2 0.5 mm, L3 1.3 mm, L4 1.1 mm). The common fibular component of sciatic nerve was mostly arisen from L4, L5, S1 and S2 (84.0%, thickness L4 0.9 mm, L5 2.0 mm, S1 2.1 mm, S2 1.2 mm). The tibial component of sciatic nerve was mainly arisen from L4, L5, S1 and S2 (96.0%, thickness L4 0.9 mm, L5 1.9 mm, S1 2.2 mm, S2 1.9 mm). The superior gluteal nerve was commonly derived from L4, L5 and S1 (56.0%, thickness L4 0.7 mm, L5 1.1 mm, S1 0.9 mm). The inferior gluteal nerve was comprised of L5, S1 and S2 in several cases (54.2%, thickness L5 0.9 mm, S1 1.3 mm, S2 0.8 mm). The posterior femoral cutaneous nerve was composed of S1 and S2 in higher freqeuncy (40.0%, thickness S1 0.9 mm, S2 1.0 mm, S3 0.8 mm). The perforating cutaneous nerve was arisen from S2 and S3 in higher frequency (56.0%, thickness S1 0.7 mm, S2 0.9 mm, S3 1.1 mm). The pudendal nerve was derived from S3 in many cases (52.9%, thickness S3 1.5 mm). These anatomical results may be helpful to predict the spinal nerve root lesions of the lumbosacral plexus.