Traditionally this was called ‘cot death’ and implies that a baby has been found dead for no obvious reason, usually between the ages of 1 month and 1 year. Amongst them will be some babies where a definite cause is found at post-mortem examination, for example an overwhelming infection, an undiagnosed. metabolic disorder or congenital abnormality or for a small number infanticide. The remaining babies, for whom it is not possible to give a cause of death, the term SIDS, or sudden infant death syndrome, is usually stated on the death certificate. Although the reasons are not fully understood, some factors which put babies at a greater risk are known; the most important is placing them down to sleep prone (on their front) rather than their back. Others include babies who were premature, those of very young mothers or whose parents smoke and babies sleeping with too many clothes in too hot a room. More deaths occur in winter than summer, breast fed babies are less likely to die, and there is some evidence that having a dummy reduces the risk. Well over 1,500 such cases are thought to have occurred in the United Kingdom each year until 1992, when government advice was issued about laying babies on their backs. The figure is now about 300.