The UK paediatric early warning score (PEWS) was developed for inpatients, looking at admission to the HDU and PICU and trying to produce a system which would recognize those children at risk of admission. Since the introduction of the '4-h wait', accident and emergency (A&E) departments have been under increasing strain to assess, treat and admit patients (if required) as quickly as possible. We designed this study with the view of identifying if the PEWS score could be used as a triage tool, to detect those patients who will need admission and therefore speed up the process of admitting children to the ward. All patients who visited A&E from 1st October-16th October 2006 were audited. The PEWS scores were collated after the study period. 774 children attended A&E during the study period. 316 patients were sent home from triage following nurse-led treatment or sent to another facility. Of the 458 patients remaining, 424 (93%) were included in the study - the only exclusion criterion was the failure of complete documentation of observations. The sensitivity [the probability of a child being admitted with a score of (n)] and the specificity (the probability of a patient not being admitted with a score of 0) were calculated. For all children aged 0-16 years, a PEWS score of >or=4 had a sensitivity of 24% and a specificity of 96%. A PEWS score of >or=2 had a sensitivity of 37% and a specificity of 88%. PEWS is of limited value in predicting admission (in a triage setting) in a population of undifferentiated disease. However, a low PEWS score has a high specificity, that is, a patient scoring <2 is unlikely to need admission.