Abstract: The invention relates to a gas-cooled rotor for an electric machine. At each axially separated rotor slot, cooling ducts are supplied with cold gas by the duct of a lower cavity and form a parallel network in the upper levels (B) of the slot cavity (1). Said network includes a radial inlet duct (6), a plurality of transverse ducts (8) constituted by grooves in the conductor strips and a radial outlet duct (7) so as to increase the heat exchange surface at these upper levels and to avoid excessive heating thereof despite the heating of the gas in the lower levels (A). Application to turbo alternator rotors.