A grounding system is provided for an electrical connector assembly which provides an interconnection between a PC card and a main printed circuit board. A header connector is mounted on the main printed circuit board and receives the PC card. Mating terminals are provided on the header connector and a receptacle connector on the PC card for interconnection of the PC card to electrical circuit traces on the main printed circuit board. At least one header grounding contact is mounted on the header connector adjacent to but spaced from the terminals and coupled to a logic ground circuit on the main printed circuit board. A card grounding contact is mounted on the PC card near the front insertion end thereof for engaging the header grounding contact and commoning the logic ground circuit of the main printed circuit board to a logic ground circuit on the PC card to provide a low impedance ground return.