One hundred and thirty four ambulatory children with bronchial asthma were investigated in the Pediatric Pulmonary-Allergic Service. In 95 patients an interval characterised by prodromal respiratory symptoms (cough, rhinorrhoea, and wheezing), behavioural changes (irritability, apathy, anxiety, and sleep disorders), gastrointestinal symptoms (abdominal pain and anorexia), fever, itching, skin eruptions, and toothache preceded the onset of the attack of asthma. Each child had his own constant set of prodromal findings. A significant age related increase in serum IgE concentrations was observed in these patients. No such relation was observed in children with an acute onset of attack of asthma without any preceding symptoms. We suggest that awareness of these prodromal symptoms may lead to an early introduction of treatment, thus avoiding or abbreviating some of the acute attacks of asthma.