Results from three tests using radio frequency (rf) electromagnetic energy to heat oil shale are presented in this report. A block of Green River oil shale 18 x 20 x 20 inches which contained 23.5 gallons of oil per ton of oil shale was heated. The first test was conducted at 1500 watts forward power at a frequency of 450 MHz. The block was heated almost uniformly, but, as predicted by the University of Wyoming rf retorting mathematical model, 1500 watts was not sufficient power to retort the block. Temperatures of 350 to 400/sup 0/F (175 to 205/sup 0/C) were attained throughout the shale block. Comparisons of calculated with measured temperatures showed fairly good agreement for the first 12 hours of the test with actual temperatures lower than calculated for the remainder of the test. The shale block was examined after the test and found to be extensively fractured. The second test was conducted at 2200 watts with a frequency of 450 MHz. The block appeared to be heating at a rate which would have retorted the shale when the rf generator broke down at 36 hours into the test. The third test was conducted at 1500 watts with a frequency of 2450 MHz. The higher frequency concentrated power into a small portion of the block and retorting was observed immediately after power was turned on. The shale block was heated to 1300/sup 0/F (705/sup 0/C) in a small area near the monopole. An impedance matching problem, attributed to dielectric breakdown, was observed at 17 hours into the test which interrupted heating for about two hours. At 29 hours into the test the monopole melted off and the test was terminated. The series of tests met the initial test objectives, which were to gain experience with the rf equipment while heating oil shale and acquire data for use in testing the University of Wyoming rf retorting model. 8 refs., 17 figs.