Increasing public awareness of the prone sleeping position, maternal smoking and overheating as potentially avoidable risk factors for the sudden infant death syndrome (SIDS) has been accompanied by a dramatic reduction in mortality. The results of two population based studies of SIDS in Avon are compared; the first one occurred before these risk factors were widely known and during the second study there was a gradual increase in publicity. Between the studies the prevalence of prone sleeping in the control populations fell significantly from 60% to 28% and almost all of the reduction in SIDS mortality (3.5 to 1.7 per thousand live births) could be attributed to this change. Other changes were also found: the seasonal pattern of incidence was lost, the proportion of expreterm babies increased and the male predominance was accentuated. The relative importance of smoking and bottle feeding appeared to increase whereas the odds ratios for heavy wrapping and overnight heating were no longer significantly elevated. Small numbers limit the significance of these individual variations but demonstrate that changes are occurring. Local and national public health campaigns have been launched in the UK and abroad to encourage infant care practices that reduce the risk of SIDS. Monitoring the effectiveness of these campaigns is important and may allow new risk factors to be identified which could in turn be targeted in future preventative campaigns. Significant reductions in mortality have followed these initial campaigns but in order to maintain them the message must be regularly renewed using an appropriate approach and effective channels of communication to target high risk families within the community.