Gases that are evolved, as eastern oil shale is heated from 150/sup 0/C to 900/sup 0/C, have been monitored by mass spectrometry. Profiles of gas evolution as a function of retort temperature are reported for CO/sub 2/, CO, Ch/sub 4/, H/sub 2/, C/sub 3/H/sub 8/, and H/sub 2/S. Over the temperature range associated with oil production, less H/sub 2/ is produced at increased heating rates. The Sunbury Shale (Mississippian age) and the Cleveland Member of the Ohio Shale (Devonian age) have very similar gas evolution profiles over this temperature range to within the experimental precision of or - 5 percent. Hydrogen and methane evolution profiles of eastern oil shales are qualitatively intermediate between those of coal and western oil shale. The low carbonate content of eastern shales makes it possible to observe char gasification by the water liberated from mineral matter. In the case of western shales, the reaction is masked by mineral carbonate decomposition. The comparison of the rate that specific gases are evolved from eastern shale, western shale, and western Kentucky coal gives some additional insight into the similarities and differences that these fuel resources exhibit.