Abstract: A modular animal cage that may be formed to enclose an area of any given size and which may be used for a wide variety of purposes. A skeletal module is formed by four upstanding corner post members interconnected by eight horizontally extending rods disposed in sets of two. A cage may be formed from the skeletal module by clipping side panels onto the rods forming the sides of the skeletal module. Top and bottom panels may also be provided. The area enclosed by the cage can be expanded by connecting one or more other skeletal modules together in side-by-side open communication.