AbstractThoracodorsal nerve distributes to the latissimus dorsi muscle. The aim of this study was to investigate the anatomic variation of the spinal nerve compositions of thoracodorsal nerve and to confirm which spinal nerve is a main component in participating amount. The most frequent type was consisted of C7 and C8 in 60%. Next frequent type was C6, C7, and C8 in 25%. Third type was C6 and C7 in 10% and fourth type was C7 alone in 5%. The diameter of each spinal nerve comprising thoracodorsal nerve was 1.20 ± 0.23 (mean ± SD) mm at C7, 0.43 ± 0.15 mm at C8, and 0.33 ± 0.09 mm at C6. These results show that the C7 nerve was the main component of thoracodorsal nerve and the anatomic variation appeared at the spinal nerve that participate by small amounts, as be excepted (C6 and C8). Clin. Anat. 20:660–662, 2007. © 2007 Wiley‐Liss, Inc.