A pilot study of 50 consecutive unselected cases of the year 2010 revealed a low rate of reporting (10.8%) of selected perioperative events related to anesthesia (specifically: hypotensive, hypertensive, bradycardic, tachycardic, and hypoxemic episodes). Consequently, the current extensive study with more representative sample size was initiated. To gain insight into possible causes (among others: time pressure, unclear definitions, fear of litigation), interviews with anesthesia staff are performed and will hopefully provide a basis for possible improvements. For the time being and considering the common nature of possible causes, the investigators suspect that their results may not be specific for their institution. The incidence of perioperative events may be grossly underestimated if the process of data collection is not properly designed and monitored.