One hundred and ninety children with atopic eczema were studied prospectively for two and a half years. The mean period of observation was 13 months. Seventy six children (40%) had between them 164 episodes of exacerbation of eczema due to bacterial infection, and in 52 (32%) infection recurred within three months of a previous infection. Twenty five episodes (15%) led to admission to hospital. Staphylococcus aureus was recovered in 97% of episodes, in combination with beta haemolytic streptococci in 62%. Physical signs suggesting infection were pustules, crusting, and a weeping discharge, but these signs alone are not diagnostic, and an exacerbation was only attributed to infection if there was a response to anti-infective treatment. Exacerbation of atopic eczema due to bacterial infection is common, the physical signs of infection are not always clear, and there is a case for a trial of oral antibiotics in any child with troublesome atopic eczema.