A whole-body inhalation exposure chamber was designed and constructed that provided for uniform distribution of aerosols within the chamber and facilitated animal care. Animals were permanently housed in the chamber while on experiment. The entire chamber (including cage units) was sanitized in a cagewashing unit. Animals and their feed were easily observed since cages were mounted in pull-out drawers. The chamber accommodated 360 mice, 196 rats (depending on size), 312 hamsters, 60 guinea pigs or 30 rabbits (the latter for exposure only). A special feature of the design was that cages and their associated excreta pans were equally spaced from chamber walls and arranged in offset vertical columns. This arrangement prevented excreta from dropping on animals in lower tiers.