OBJECTIVES--To determine whether a modified paediatric resuscitation reference chart improves the speed and accuracy of calculation of doses of drugs in simulated paediatric cardiopulmonary arrests when compared with the chart devised by Oakley. DESIGN--A prospective study in which a series of randomly assigned questions was used to compare the performance of doctors using the two charts. SETTING--Accident and emergency departments in two hospitals. SUBJECTS--31 senior house officers. MAIN OUTCOME MEASURES--The speed and accuracy of calculation of volumes of drugs to be administered. RESULTS--The modified chart significantly increased the accuracy of the calculations (62/62 v 43/62, p < 0.01 [corrected]), the speed of correct calculations (6.8 v 36.0 s, p < 0.0001), and the number of calculations that were completed (62/62 v 50/62, p < 0.001). CONCLUSIONS--The modified paediatric resuscitation chart should supersede the existing chart.