With the decline of the former main causes of death in early childhood--infections and starvation--sudden infant death syndrome (SIDS) has emerged as the most important single cause of postneonatal infant mortality. It has adopted the role of a major indicator for the standard of public health care. Despite extensive input into research, its pathophysiology has remained rather obscure. The resulting helplessness of scientists and health care professionals have lead to adherence to unconfirmed pathophysiological hypotheses and to pursuit of preventive strategies of doubtful efficacy. In this overview, the medical and technical background of five major hypotheses is being presented. A lot can be learnt from the history of their development, efforts to refute them, and the reasons for unreflected adherence to them. (1) Due to its illustrative nature, the so-called 'status thymico-lymphaticus', the theory of asphixation by an enlarged thymus, could not be eradicated although well-reknowned physicians--including the Austrian pathologist Paltauf--have repeatedly attempted to do so. (2) Assumed familiarity, an aspect which attracted the attention of pediatricians to SIDS initially has been excluded, but an increased risk of SIDS for the siblings of affected babies is still common belief. (3) The sleep-apnea-hypothesis has turned out a complete error with serious consequences, but home apnea monitors are still being widely recommended. (4) The rise of SIDS in the 80ies and its subsequent decline in the 90ies has been interpreted as the advent and successful control of an epidemic although significant numbers of cot death have been reported long before the turn of the century, and the apparent increase which paralleled the introduction of the 9th edition of the ICD code is most likely due to improved registration. (5) Finally, SIDS is still being considered a random event--ignoring all evidence of an obvious role of socioeconomical factors.