International studies show that children in day care centres have approximately twice as many episodes of infectious diseases as children cared for at home, while, according to most studies, children in family day care experience an intermediate number of infections. After some months in day care the risk of infection decreases. The diseases in question are usually transferred from person to person through close physical contact. Children's general mode of behaviour tends to favour such transmission. The risk of infection in pregnant women on the day care staff and among parents is considered. Finally, the author discusses the potential to control infection in a day care setting. Strict rules for isolation of sick children probably have little effect on the spread of the infections. Good routines for washing hands and for changing nappies are considered to be the most important ways of controlling infection in day care centres.