Static, nitrogen, and steam sweep pyrolysis, and co-pyrolysis of oil shale and Seyitomer lignite were studied. A modified Heinze type retort with a 40 g sample capacity was used. Pyrolysis runs were started at room temperature; samples were heated at a rate of 4-degrees-C/min up to 550-degrees-C, and held for 30 min at this temperature. Both nitrogen and water sweep improved the oil yield considerably compared to static pyrolysis. Steam had a greater effect on oil yield. The changes in oil structure were similar for nitrogen and steam: increases in sweep velocity caused increases in aliphatics and aromatics at the expense of polar compounds. Co-pyrolysis of lignite and oil shale had a synergistic effect on yield which was small compared to the sweep effect. This oil shale-lignite synergism disappeared at high sweep velocities.