The purposes of this study are to determine partitioning of Hg, As, and Se among spent shale, shale oil, retort water, and offgas during the retorting process and to identify Hg, As, and Se species in shale oil, retort water, and offgas. These species were investigated in eastern and western shales retorted at slow (1 to 10/sup 0/C/min) heating rates to final temperatures of 500 and 750/sup 0/C. The evolution of Hg in the offgas during retort run PNL-2 occurred in two clearly defined stages, with elemental Hg appearing first followed by the organomercury. During the initial stage of Hg release into the offgas, 87% (4 ..mu..g) was identified as elemental. The organomercury appeared at the later stage of Hg evolution in the retort run, accounting for more than 99% (126 ..mu..g) of the mercury in that sample. In general, more than 90% of the As remained in the shale after retorting. The As in the western shale demonstrated a slightly greater tendency to mobilize into the liquid products than did the As in the eastern shale retorted under similar conditions. The As that mobilized preferentially redistributed into the shale oil rather than the retort water in both eastern and western shales, and the redistribution into the liquid products appeared to increase with higher heating rates and maximum temperatures. No As was observed in the offgas during any of the three retort runs monitored. In general, more than 80% of the Se remained in the shale after retorting. The selenium in the eastern liquid products slightly favors partitioning into the retort water. Selenium in the western liquid products is preferentially redistributed into the shale oil. 15 refs., 10 figs., 2 tabs.