Objective To improve the Manchester Triage System (MTS) in paediatric emergency care. Methods The authors performed a prospective observational study at the emergency departments of a university and teaching hospital in The Netherlands and included children attending in 2007 and 2008. The authors developed and implemented specific age-dependent modifications for the MTS, based on patient groups where the system's performance was low. Nurses applied the modified system in 11 481 (84%) patients. The reference standard for urgency defined five levels based on a combination of vital Results Compared with the original MTS specificity improved from 79% (95% CI 79% to 80%) to 87% (95% CI 86% to 87%) while sensitivity remained similar ((63%, 95% CI 59% to 66%) vs (64%, 95% CI 60% to 68%)). The diagnostic OR increased (4.1 vs 11). Conclusions Modifications of the MTS for paediatric emergency care resulted in an improved specificity while sensitivity remained unchanged. Further research should focus on the improvement of sensitivity.