The hydraulic distributor, more particularly for power steering systems of vehicles, comprises two rotary members (1-3, 9) which are so designed as to form a substantially disc-shaped cavity (8) divided up in at least one pair of working chambers (28) by arms (13, 14) belonging to one (9) of said members (or rotor). These arms cooperate with inlet (18) and outlet (24) ports in the other member (1) (or stator) so as to form control valve means for controlling activation fluid flow supplied from a pressure generating source (26). The rotor (9) has at least one intermediate arm (33) which extends into each of the chambers of the pair of working chambers (28, 43) and which cooperates with fluid passage ports (36) in the stator in order to form additional fluid flow control valve means. The first portion (of zero slope) of the torque/activation pressure curve of the distributor is controlled by the closing edge (41a) of the intermediate arm (33a) oriented towards the arm ( 14) which is associated with the outlet port (24) and also by the closing edge (38) of the arm (14) which is associated with outlet port (24) which closing edge is oriented towards the intermediate arm (33) extending into the preceeding working chamber (28, 43a).