Comparison of perinatal, environmental and infant care factors in communities with different Sudden Infant Death Syndrome (SIDS) incidences could reveal ways of reducing SIDS frequency in the higher incidence community. The incidence of SIDS in Sweden is much lower than that in Adelaide. Several factors known to be significant in SIDS are less common in Sweden: teenage mothers, low birthweight and the failure to immunize infants. The most striking difference is the absence of the winter peak in Sweden. In Sweden almost every infant sleeps in a heated environment in winter, whereas in Adelaide most do not. This report discusses ways in which the Adelaide winter peak may be avoided. There is a lower incidence of SIDS in communities that invariably use the supine sleeping position for infants than in those who do not. Abandoning prone sleeping for infants in Adelaide should reduce the incidence of SIDS.