Abstract: A radioreceptor assay for benzodiazepines in saliva which comprises measuring the diminution of attachment of a known quantity of radio labeled benzodiazepine to a receptor carrier in the presence of an unknown quantity of unlabeled benzodiazepine in a known amount of human saliva. Benzodiazepines are selected from the following oft-utilized drugs which are also representative types of benzodiazepine; namely, diazepam (Valium), chlordiazepoxide (Librium), nitrazepam (Benzalin), oxazepam (Serax), flurazepam (Dalmane), and clorazepate.Competitive receptors suitable for the present benzodiazepine radioreceptor assay are from fresh rat frontal cortex. Utilizable receptors are whole brain cortex, human cortex, and striatum.