The recent emergence of the critical problem of groundwater contamination due to materials leaching from toxic waste disposal sites and other sources has had a sobering impact on society. The rash of unexpected contamination has led to a plethora of legislation designed to address this problem. Along with this legislation has come the need to be able to accurately, effectively, and economically detect the contamination of groundwater. The primary objectives of the research reported here were to investigate the use of the parameters total organic carbon (TOC), total organic halide (TOX), and the photoluminescent bacterial bioassay, Microtox (Beckman Instruments, Carlsbad, CA.) as screening parameters for the evaluation of groundwater quality. This objective was accomplished through an analysis of background information from the literature including a Virginia State Water Control Board study of groundwater quality in Southwestern Virginia, a laboratory study, a United States Department of Agriculture groundwater project, and analysis of five field samples collected from uncontaminated and contaminated sources. The TOC and TOX tests were shown to provide important information. Microtox bioassays were performed on all samples and the results were correlated with the chemical analysis. It was concluded that the Microtox bioassay was a useful screening test for groundwater quality and that this assay in combination with the TOC and TOX parameters provided a reasonable indication of groundwater quality. / M.S.