Diagnosis of acute poisoning is based on history, symptoms, biomedical investigations, toxicological analyses, and sometimes therapeutic tests. Toxicological analytical methods are now widely available. A qualitative or semiquantitative analysis of the parent compound may be adequate for diagnostic assessment. A quantitative analysis is mandatory for kinetic studies. For instance, in ethylene glycol poisoning, analysis of ethylene glycol concentrations is useful for the diagnosis, but glycolate concentrations are more relevant for the evaluation of the severity and prognosis. Groups of symptoms (or toxidromes) may provide diagnostic clues for toxins that are not usually included in routine screening. The management of the poisoned patient is mostly supportive, but toxicological quantitative analyses are mandatory for some treatments, e.g. alkaline diuresis in salicylate poisoning, repeated activated charcoal in theophylline poisoning, haemodialysis, ethanol in ethylene glycol poisoning, or the use of chelating agents.