The prone position is thought to be an important factor in the sudden infant death syndrome (SIDS). The sleep positions of unselected infants aged 6 months and younger attending clinics in the Cape Peninsula were studied; 62.4% slept prone with the face to the side. This position differs between the ethnic groups (whites 50.0%; blacks 58.7%; coloureds 69.8%) and the respondents' social class (higher classes 54.1%; lower classes 69.2%). The sex of the baby, the sleeping place and the educational level of the mother did not influence the position used. Ninety-four per cent of black infants slept with their mothers compared with 71% of coloured and 4% of white babies. The study confirmed that there are cultural differences in sleeping positions adopted by infants. The role this plays in SIDS among different ethnic groupings still needs to be clarified.