The investigation reported herein concerns the development and evaluation of a pneumatic barrier for restraining the natural flow of surface oils in the Buffalo River. The initial phase of this study involved laboratory experiments to evaluate the surface currents produced by bouyant air-water plumes which were formed by the injection of air through single and multiple orifices submerged below the water surface. Based upon the data obtained in the laboratory experiments, a full scale, prototype air barrier system was designed. This barrier system was built and installed in the river. A full scale test program was initiated in order to evaluate the performance of the barrier. Following the river test phase of the program, additional laboratory tests were conducted in a water channel facility to investigate the performance of a barrier system at higher currents and for different oil types than were available in the Buffalo River. It was determined that a pneumatic barrier could be an effective device for stopping the flow of surface oils for currents less than one foot per second. The actual limiting speed for a particular oil was a function of its viscosity and specific gravity. In no instance was any oil that was tested restrained in a current of more than 1.5 fps.