Damage to the dorsomedial branch of the medial dorsal cutaneous nerve is not uncommon in surgery of the hallux. The resultant morbidity can be disabling. In the light of the senior author’s operative observation of a sentinel vein, we undertook a cadaver study to investigate the anatomical relationships of the dorsomedial branch of the medial dorsal cutaneous nerve. This established that in 14 of 16 cadaver great toes exposed via a modified medial incision, there is an easily identified vein which runs transversely superficial and proximal to the nerve. In a prospective clinical study of 171 operations on the great toe using this approach, we confirmed this anatomical relationship in 142 procedures (83%), with no complaint of numbness or pain in the scar at follow-up. We attribute this to careful identification of the ‘sentinel’ vein and the subjacent sensory nerve, which had been successfully protected from damage. We recommend this technique when operating on the great toe.