This investigation concerns the practicability of using the dimethyl silicone polymer fluids as lubricants in unilaterally loaded journal-bearing machines. A specially designed bearing machine was used having forced-feed lubrication up to pressures of 26 psi. It was operated at a speed of 1725 rpm, and the oil-sump temperatures varied from 115 to 130 F, while the bearing temperatures varied from 150 to 240 F. Plain or chrome-plated high-carbon-steel shafts were used in conjunction with bearings of copper-lead, bronze, tin-base babbitt, cast iron, commercial brass, aluminum (17S), copper and Alfin metal. Cast-iron or steel bearings used in conjunction with steel journals were entirely unsatisfactory when lubricated with the silicone fluid. All of the nonferrous bearings performed satisfactorily with the silicone fluid. It was found that an organic silicon-containing film was formed during the long, slow, break-in process. The need for such a long break-in could be eliminated by the application of a technique of pretreating or lacquering the bearings with silicone oil before assembling the test machine. The method of pretreatment is described briefly. It was also discovered that such pretreated bearings were able to carry much higher than normal loads when operated in contact with petroleum lubricating oil.