The arterial supply to the flexor tendons of the fingers was studied by means of angiography, by the injection of coloured latex, and by microdissection. It was established that there were no anastomoses between the intra-osseous circulation and that of the synovial sheath. Two separate sources of blood supply to the sheath were found: the digitopalmar arches and the specific arteries of the sheath. The findings indicate that the ideal location for incision into the digital sheath is in the midline of the palmar surface. The flexor tendons within the sheath are supplied only by branches of the digitopalmar arches. Considerable differences were observed in the details of blood supply of the tendon of flexor superficialis and that of flexor profundus.