Biochemical and pharmacological tests usually prescribed in casualty department were reviewed taking into account their physiological significance and predictive value : ions, total proteins, carbohydrate and nitrogenous metabolites, enzymes, tissue markers, pharmacological drugs. Few blood components were kept with the first intention, ideally with a turn around time below one hour: sodium, potassium, chloride, bicarbonate, total proteins, pCO2 and pO2, creatinine, glucose, ketone compounds, calcium, bilirubin, transaminases, lipase, C-reactive protein, myoglobin, troponin, chorionic gonadotropin hormone. Those tests do not have to be systematically performed but prescribed only after the evaluation of pre-test probabilities by the clinician.