Hypothermia is a possibility to reduce the amount of brain injury in asphyxiated newborn infants. The historical analysis demonstrates that the paradigm of cooling newborns is only revived half a century after its first application. Evidence for its neuroprotective effect mainly stems from animal experiments. The few publications on the application of hypothermia in newborns describe surprisingly few side effects. Randomized, controlled trials are in process,which achieve a mild hypothermia of body core temperatures of 33.5 to 34.5degreesC over three days either by cooling the body from the head and synchroneously warming the rest of the body, or by a cooling mattress. The diagnosis and prognosis of asphyxia and its consequences is best achieved by the use of the amplitude-integrated EEG serving as indication for the application of hypothermia. Measuring a brain temperature and controlling the degree of hypothermia remain unsolved problems. The uncertainty of the prognosis as well as the difficulty of impacting decisions pose enormous ethical problems to parents, doctors and nurses.