Pillars surrounding modified in situ retorts contain large amounts of potentially recoverable shale oil. Recovery of the oil contained in the pillars within a few feet of the retorts would significantly increase oil yields. A series of tests was conducted to evaluate methods for recovering oil from pillars. Analysis of core samples taken from a block of western oil shale that was retorted using radio frequency energy indicate oil did not move horizontally within the block, but may have moved vertically by gravity drainage. In a later test, a block of western oil shale was extensively fractured when the block was heated to 120 to 150·C (250 to 300·F) using radio-frequency energy at a frequency of 915 MHz. Attempts to retort the fractured block by retorting oil shale rubble adjacent to the block were not successful. Channeling of the retorting air prevented the rubble from being heated as hot or as long as was planned. Another block of western oil shale was retorted with radio frequency energy to acquire data to use for testing the Baker-Jarvis retorting model at a frequency of 915 MHz. The 915 MHz generator failed after 92 hours of heating with temperatures in the block varying from 450 to 320·C (840 to 61O·F). Heating was continued for 6 hours using a frequency of 2450 MHz until dielectric breakdown was observed immediately after lightning struck nearby.