[en] Four benzodiazepine radioimmunoassays are described, the most sensitive of which can detect sub-therapeutic levels of bromazepam, chlordiazepoxide, clobazam, demoxepam, desalkylflurazepam, desmethyldiazepam, diazepam, flunitrazepam, lorazepam, medazepam, nitrazepam, oxazepam, prazepam, temazepam and triazolam. The standard curve for diazepam has a concentration range of 0-2.5 ng ml^-1. The assay is particularly applicable to blood samples of forensic interest that may be haemolysed or decomposing. A 75 μl sample is required. The antiserum and [³H]flunitrazepam used are commercially available. (author)