Knowledge of the blood vessel supply of the flexor sinews has been considerably enlarged by micro-angiograms. Arrangement of the vessels in the non-tendinous area of the hollow hand is different from that of the osteofibrous channels. The digitalis propriae form arcades, of which the vincula longa and brevia are responsible for segmental supply of the two flexor sinews at the triphalangeal fingers. Tendinous areas without vessels and poor blood supply are most probably supplied by means of diffusion. The intratendinous arrangement of the vessels has led to a change in suturing technique. The long flexor sinew of the thumb is supplied by blood vessels in the thenar region and at the base of the end phalanx.