Diazepam was detected in 26% of cases of people suspected of driving under the influence of drugs in Sweden, and its active metabolite nordazepam was detected in 28% of cases. Other benzodiazepines and zolpidem and zopiclone also were found in high numbers. Many drivers had blood levels far exceeding the therapeutic dose range, suggesting a high degree of potential for misuse for benzodiazepines, zolpidem, and zopiclone. In Northern Ireland, in cases where drugs were detected in samples from impaired drivers who were not impaired by alcohol, benzodiazepines were found in 87% of cases. Diazepam was the most commonly detected benzodiazepine.