Abstract: A ventilated animal cage rack has a hollow housing divided into a plurality of horizontally-disposed shelf compartments separated from each other by partition walls and having front open ends normally closed off by transparent doors which isolate the interiors of the shelf compartments from each other and from the interior of the room containing the cage rack. Each shelf compartment is sized to contain a row of horizontally-spaced animal cages having open top ends and closed bottom ends, with the open top ends spaced well below the ceiling of the shelf compartment. A low pressure air plenum extends vertically along one side of the cage rack and communicates with one side of each of said shelf compartments, the other sides of which contain air inlet openings communicating with the room interior, thereby providing a low-pressure negative air flow along the top open ends of the contained animal cages to said air plenum and then to a room exhaust system.