Definition of the problem: Every decision for or against life-sustaining measures in ICUs is a result of different factors, the kind and course of the illness, probable prognosis, age of the patient, but also character, experience and knowledge of the acting staff members. These factors may combine in an accidental way. The aim of the investigation was to evaluate these factors as far as possible. Arguments and conclusion: 287 physicians from intensive care units (ICU) in 43 hospitals were interviewed. In a questionnaire, 6 case vignettes of severely ill patients served for hypothetical reasons and eventually decisions to act. Maximum medical activity was recommended in university hospitals, but acute lifesustaining measurements were equally accepted in all three kinds of hospitals. Other factors - such as duration of medical activity of the doctors, years of experience in intensive care medicine, motivations to act, sex and life attitude, but also the age of the patients - were of no significance. Because of the traditional close cooperation in ICUs, the nursing staff was also interviewed. For reanimation, intubation/artificial ventilation and pain relief therapy there where no differences in the group of doctors. These were significant in invasive diagnostic and therapeutic measurements, which were generally rejected earlier and more easily by the nursing staff.