Some five years ago, during the development of the new and enlarged Department of Radiology at St. Joseph Hospital (Fort Worth, Texas), the desirability of exposing and processing radiographs in various parts of the hospital became apparent. Particularly in the orthopedic and urologic operating rooms was the need of immediate processing facilities evident. Financially, however, the provision of fixed developing tanks in closets adjacent to these rooms was impractical. Various types of portable processing equipment were checked but, because of weight, limitation of film size, and other considerations, none were thought feasible. The design of a mobile tank that would answer the varying needs of these departments was therefore undertaken. The tank was designed with the advice of Mr. M. B. Thompson of Eastman Kodak Company and Mr. H. O. McKenzie of the General Electric Company X-Ray Department. The Reliance Engineering and Manufacturing Company in San Antonio worked out the details and undertook the construction. The tank has now been in use for some four years, and has been found very satisfactory. When the same need was encountered at the Harris Memorial Hospital, another tank with certain modifications was built. This new tank has been in service for a year and has proved satisfactory in every respect. The tank is a standard 5-15-5 splashproof type. It measures 21 × 21 inches, is 45 1/2 inches high, and will handle any standard size hanger. It is mounted on 6-inch casters and covered with a stainless-steel top, having a heavy rubber liner, which is clamped on with trunk-type locks. When locked, this liner seals the five-gallon inserts to prevent the splashing or mixing of chemicals in transportation. The force expended in moving the tanks is less than that necessary for a small mobile x-ray machine. Heating is by electric elements in stainless-steel inserts in the lower part of the water chamber. A thermostat is located in the mid-portion in the wall of the tank, at the same distance from the water as the solutions, in order that a uniform temperature may be maintained. Indicator lights with small red and amber jewels, at the lower right hand front, show red when the tank is heating and amber when it is at the desired temperature. Storage compartments are available under the tank for film boxes and cassettes of various sizes. On the right side of the tank is a towel ring; on the left side are hooks to carry the desired number of film hangers. On the left hand front is a valve connected to a polyethylene tube, which can be put in a floor drain and used to drain the solutions and clean the tank. An adjustable safe light in the right rear of the tank, with a sixty-second interval timer attached, is used in the processing of films. While in storage, this tank can be plugged in at all times, the thermostat maintaining any desired temperature. With the top clamped on, there is practically no oxidation or heat loss.