We examined hospital and domestic infant care practices in Oxfordshire and Northampton Health Districts to measure changes in prevalence of sudden infant death syndrome (SIDS) risk factors, and to evaluate a specific educational intervention restricted to Oxfordshire. We sent a postal questionnaire to 2781 parents of babies newly born in January 1992, July 1992 and January 1993 and achieved an 88% response rate. Overall, in hospital a relatively constant proportion (81%) slept on their sides and few prone, whereas at home 52% (but increasing) slept supine and 8% prone part or all of the time. Significant differences existed by district, both in hospital and at home, with more sleeping supine in Oxfordshire and more side-sleeping/propping in Northampton. First-time parents were more receptive to safety guidelines about sleeping position and several other risk factors also. We detected no modifying effect of the Oxfordshire advice. Professional practice can influence parental behaviour but general media coverage may produce the biggest effects.