Recent data suggest that desmethyldiazepam (DD), a major metabolite of several benzodiazepines (BZD), might be of natural origin. Therefore we tried to quantify DD and diazepam (D) in animals during maturation (e.g. hen, chicken, eggs), in brain of species at different evolutionary stages e.g. salmon, frog, monitor/reptile, rat, cat, dog, deer, bovine) including newborn and adult humans. Since low concentrations of DD (range 0.01-0.04 ng/g wet wt) and D (range 0.005-0.02 ng/g) could be measured in different species by sensitive and specific mass spectrometry (GC-MS), we analysed also several plants (e.g. maize corn, lentils, potatoes, soybeans, rice, mushrooms). Again, DD and D could be detected in low amounts (0.005-0.05 ng/g) in some plant products. This would suggest that DD and D might be of natural origin and incorporated via the foodchain into the animal and human body. The biological role or clinical relevance of these intriguing findings need still to be elucidated.