Abstract: A fluid cooling system for electronic systems particularly adapted to cool large scale integrated circuit chips mounted on substrates. The system has one or more heat exchangers through which a liquid coolant is circulated. Each heat exchanger has a flexible wall and is mounted so that its flexible wall is in close proximity to a surface of the substrate to be cooled. A low thermal impedance contact is made through the flexible wall of the heat exchanger between the substrate to be cooled and the coolant flowing through the heat exchanger because of the pressure of the coolant in the heat exchanger. The heat exchangers are connected into the cooling system through flexible conduits so that a heat exchanger can readily be moved out of contact with a substrate without disrupting the flow of coolant through the cooling system.