In many experimental and research projects involving odor evaluation and measurement, there is the need for a suitable enclosed space in which to conduct panel tests and to simulate actual conditions as realistically as possible. This has long been recognized by workers in the field, and a considerable amount of time and effort has gone into the design and construction of odor test rooms. During the past several years, the Flavor Laboratory of Arthur D. Little, Inc., has had the opportunity of working very closely with the American Gas Assn. on the development of a test room to further the particular odor studies being sponsored. The success of the test room and the degree to which its use advanced the problem at hand has led us to believe that the basic features may well have direct application in a great diversity of odor studies. It is difficult to arrive at the universal test room—one that would fill all the requirements and would fit the needs of all odor situations. This sweeping claim is not made for the room described. The information about the odor test room is presented primarily for the consideration of the workers in this field. Four of the principal variables involved in test rooms have been singled out for specific discussion at this time. They are as follows: 1. The design of the room, including the general layout and size. 2. The room construction, including the materials used. 3. The auxiliary equipment outside the test room, including sample-measuring devices, filtering systems, and exhaust apparatus. 4. The techniques used in the room operation and actual odor evaluations and measurements.