Prader-Willi syndrome (PWS) is a complex condition with many medical and psychological features. In individuals with this syndrome, causes of death were studied. Data of 27 case reports were collected. Ages at death ranged from neonatal to 68 years. None of the individuals were treated with growth hormone (GH). Most cases were not completely documented and autopsy was performed in a minority of cases only. In five cases, death was considered not to be causally related to PWS. Hypotonia with hypoventilation was noted in the babies, and acute respiratory illness with unexpected sudden death was experienced in young children with PWS. Two young children died after a short period of fever and gastroenteritis. Obesity and its complications leading to death were pronounced in the adult group. One (possibly two) adult(s) died from gastric dilatation and shock. Based on these data, some cautious conclusions can be drawn. In babies with PWS hypoventilation is a risk factor; upper airway infection may be more serious than anticipated and any other clinical features pointing to an infection should be taken very seriously. Therefore, young infants with PWS hospitalized with an upper airway infection and/or hypoventilation or gastroenteritis symptoms, should be closely monitored. Early diagnosis and prevention of overweight is a major factor in preventing early causes of death in individuals with PWS. In the adult group, weight reduction is important but difficult to manage. Sleep apnea should be recognized and treated. Pain in the upper stomach and/or vomiting should be taken as a possible sign of acute intestinal dilatation; intravenous support may be life saving.