To review routine observations on all children admitted to the Children's Hospital for Wales and the feasibility of implementing an early warning score for children developing critical illness.Nursing staff, while performing their routine duties, recorded the physiological observations of temperature, heart rate, respiratory rate and blood pressure, as well as identifying airway threat, recording oxygen saturation levels, level of consciousness using the AVPU scale (alert, responds to voice, responds to pain, unresponsive) and identifying if they had concerns about a child on a new paediatric observation chart. The clinical care policy for each ward determined the frequency of recording observations.Data were collected for 1,000 patients on whom 9,075 sets of observations were performed. Of those 9,075 sets, temperature was the most frequently recorded observation at 88.4% (95% confidence interval (CI) 87.7-89), followed by heart rate at 86.8% (95% CI 86.1-87.5), respiratory rate at 79.7% (95% CI 78.9-80.5), AVPU at 36.4% (95% CI 35.4-37.4) and blood pressure at 25.1% (95% CI 24.2-26.0). A complete set of observations needed for the Cardiff and Vale Paediatric Early Warning System to trigger effectively were only recorded in 52.7% (95% CI 52.4-53.1) of patients.There were variations in the frequency, type and recording of observations. This issue needs to be addressed if scoring systems are to be implemented. The findings of this observational study suggest that the required basic observations of acutely ill children are not being carried out.