In an effort to determine potential hindrances to the commercial development of the oil shale industry mass balance Fischer assay was used as a reference retorting method to examine the distribution of selected elements generally considered as contaminants in the final retort products. The elements examined were nitrogen, sulfur, silver, arsenic, barium, cadmium, chromium, copper, mercury, lead, selenium, and zinc. The shales used in this study were an eastern (New Albany) interim reference shale, a western (Green River Formation) interim reference shale, and a series of stratigraphically differentiated shales from Colorado corehole No. 1 in the Piceance Creek Basin. Analysis of the raw shale and retort products was accomplished using instrumental elemental methods including inductively coupled argon plasma spectroscopy and graphite furnace atomic absorption. Carbon balances indicated a high potential for achieving good mass closures existed. However, instrumental limitations combined with a high potential for contamination and/or representative sampling problems resulted in poor closures for many of the trace elements. Consistent closures were obtained for arsenic, barium, copper, and zinc. Given the operating conditions of the retort all elements under consideration remained primarily in the spent shale. Elements verified in the oil product included nitrogen and sulfur compounds and arsenic and selenium. The water product was also contaminated by nitrogen and sulfur compounds and arsenic and selenium. Evidence suggests the sulfur occurs primarily as organic sulfur. Quantitative results for the gas product were poor. However, sulfur and mercury were determined to be present at significant levels in the gas stream. The data presented here concurs with previously reported data that suggests the existence of several potential problem areas in the development of an oil shale industry. 42 refs., 1 fig., 42 tabs.