In a compressor having at least two cooperating rotors of which at least one has a screw form, the medium to be compressed is supplied through a stationary inlet port located radially outside the screw-formed rotor at the meshing zone between the rotors, where new volume on rotation of the rotors is continuously formed for sucking the medium into the compressor. The inlet port extends in the axial direction of the screw-formed rotor with a substantially constant width and shows an area which is substantially in accordance with the sum of the cross-sectional areas of the grooves of the screw-formed rotor, which grooves communicate with the inlet port and in which the medium is transported further on into the compressor.