Abstract: A system for taking samples of materials undergoing processing in a rotary kiln is disclosed in the form of a first or inner member mounted on and passing through the kiln shell and containing a chamber in direct communication with the kiln interior; a second or outer member forming an outer chamber and having one end connected to said first member; and a pivotable swing gate disposed between the inner and outer members for controlling communication between the two chambers. The outer end of the outer member has an adaptor for removably mounting a material-collecting vessel or catch can thereon. Opening of the swing gate will permit material from the kiln interior to enter the catch can without contact with the ambient environment, and subsequent closing of the swing gate permits sealing of the inner chamber in communication with the kiln interior before removal of the catch can and its contents from the end of the outer member.