Anesthetic practice is inherently risky. Adverse events associated with anaesthetic practice have been evaluated for a long time. A significant decrease in anaesthesia-related mortality and morbidity has been achieved over the last 50 years. This improvement is the result of multiple innovations such as the use of ASA classification, systematic preoperative assessment of comorbidities, color codes for oxygen and nitrous oxide cylinders, pulsoxymeters, postanaesthesia care units and devices measuring depth of anesthesia. However, the value of the evidences supporting the use of these innovations is highly variable. If the level of evidences demonstrating the effectiveness of bispectral index and other measures of the depth of anesthesia to prevent awareness is high, the evidence supporting color coding of oxygen and nitrous oxide cylinders to reduce the risk of anoxia is low. These innovations are mainly supported by common sense. However, many innovations and procedures should be more systematically assessed in order to discriminate effective from ineffective practices or devices, for the best benefit of patients.