[The nature of surgical "risk"].

: The set of unfavourable events consequent on anesthesiological treatment (or more generally on operating procedures) and commonly called anaesthesiological "risk" (or more generally operating "risk") is not a collection of contingencies but would appear to correspond to definite typologies which are discussed in the paper. Study of this subject is of particular interest at the moment when in other respects anesthesiology seems to have attained, a high level of technical maturity. In any case, even in the absence of other findings, a certain type of accident appears open to control and reduction by means of appropriate measures of organizational type. Another series of accidents seems to derive in effect from an underestimation of the impact which anaesthesiological (together with surgical) aggression produces on the patient's biological reserves. For a more through assessment of these interactions, a classification of total operating risk is proposed. While this for the moment is merely a working hypothesis, it could in the future prove an effective probability "predictor" of operating risk.