Direct burning of a diesel oil-shale slurry containing up to 2.5 wt% of diesel has been studied. We used an air-atomized nozzle mounted on the bottom of a vertical 30-cm diameter segmented combustor. The heat-transfer rate distribution to the water jacket and flame stability improved as the percentage of oil shale in the diesel fuel was increased. Stable flames were observed for up to 20 wt% of oil shale.