Immunoenzymatic test, EMIT Tox, proposed for qualitative and semi quantitative determination of toxicological levels of benzodiazepines in serum is compared with gas chromatography. When used for qualitative purposes in 102 sera, the EMIT Tox test gave 5% error. In semi quantitative determinations, the EMIT Tox test was applied to 139 sera with one or more of the three benzodiazepines (oxazepam, desmethyldiazepam, diazepam), showing a significant correlation with levels measured by gas chromatography; but the EMIT Tox test frequently yields values too low for elevated oxazepam and desmethyldiazepam concentrations.