Efficient soil bioassays are needed in a screening array to determine the toxicities of industrial products and wastes. Hydrogen consumption is a common soil microbiological process that we evaluated as a possible soil indicator of toxic effects. Elemental tritium was used as a tracer to determine the H2 oxidation rates in soils. The H2 bioassay can be completed within 24 h using liquid scintillation counting of the tritium tracer. This test was used to evaluate the effects of known toxic chemicals (e.g., heavy metals, herbicides, and air pollutants) as well as a variety of suspected environmental harmful compounds (e.g., waste waters, particulates, and sludges from industrial processes) on H2 oxidation in soils. This bioassay responded to test compounds at concentrations shown to be toxic in other soil microbiological investigations.