Fascias can be used for reconstruction of gliding surfaces of upper and lower extremities or when thin, pliable coverage is required. Free large and well-vascularised fascial flaps are not very many and harvesting is seldom onto upper limb. The aim of this work was to study blood supply of the posterior brachial fascia in order to define the anatomical bases of a new free fascial flap. Our study included dissection on 18 anatomic specimens from 10 cadavers. Measures of the flap and blood supply were studied. Histological study was performed to analyse vessels location and measures into flap thickness. The posterior brachial fascia was thin, with a broad surface area and easily separable from the subcutaneous and muscular plane. Its average surface size is 115-mm length and 54-mm width. It was richly vascularised by two major pedicles: the cutaneous posterior brachial pedicule and the fascial branch of the superior ulnar collateral artery. Satellite venous elements were always present. A rich vascular network exists within the thickness of the fascia. Surgical procedure of flap harvesting is described. Harvesting of the flap can be carried out by a posteromedial approach into upper limb, without significant donor-site morbidity. This flap is adapted to cover and reconstruct gliding tendinous surfaces onto hand or fingers.