An isolator, in which complex operations can be performed on a large gnotobiotic dog, was designed and fabricated of lightweight stainless steel. This "T" shaped chamber is 20-40 inches wide, 96 inches long, and 38-58 inches high. It has two 18-inch diameter entry ports and a pair of gloves mounted beneath each of four plate glass windows. The isolator rests on a 12-inch high stainless steel pallet and is moved about the laboratory by a portable hydraulic platform lift. It is readily sterilized in an autoclave at temperatures up to 285 degrees F (140 degrees C) and can be cleaned and resterilized in less than 8 hours. Although the isolator is more expensive than one made of flexible plastic film, it has the advantages of not being readily punctured and it requires less labor to clean and sterilize between uses. Thus, it is more secure and, in the long run, more economical.