Seven runs in a series of experiments to study the behavior of solid-recycle systems for oil shale retorting have been completed at the Lawrence Livermore National Laboratory. Two of these runs failed because of mechanical problems, but the other five succeeded in yielding useful data. By operating the small-scale recycle system described herein, we were able to produce an oil yield equal to Fischer assay and to gain valuable information about pressures, temperatures, and flow rates. We also learned that pyrolysis gas has a low concentration of sulfur-containing compounds, none of which is detectable in the combustion gas. 3 refs., 15 figs., 8 tabs.