In order to assess the significance of drug levels measured in clinical and forensic toxicology as well as for therapeutic drug monitoring (TDM), it is essential that good collections of data are readily available. For more than 400 frequently used drugs therapeutic and, if data were available, toxic and fatal plasma concentrations as well as elimination half-lives were compiled in a table including, e.g., hypnotics like barbiturates and benzodiazepines, neuroleptics, antidepressants, sedatives, analgesics, anti-inflammatory agents, antihistamines, anti-epileptics, beta-adrenergic antagonists, antibiotics (penicillins, cephalosporins, aminoglycosides, gyrase inhibitors), diuretics, calcium-channel blockers, cardiac glycosides, anti-arrhythmics, anti-asthmatics, angiotensin converting enzyme inhibitors, opioid agonists, and local anaesthetics. Data have been abstracted from published information, both compilations and primary sources, and supplemented with data collected in our own forensic and clinical toxicology laboratories. Wherever possible, ranges for therapeutic plasma concentrations are expressed as trough concentration at steady-state. The range of (or single) half-life values given for each drug are chosen to represent the terminal log-linear phase at most. In addition to the assessment of significance of drug levels for the therapeutic monitoring of patients, this list can assist the diagnostic assessment in cases of intoxication.