To compare oscillometric blood pressure devices with mercury sphygmomanometry in children. Blood pressure measurements were obtained with a mercury sphygmomanometer and one of two oscillometric devices. Correlations within each device and agreement between the two devices were evaluated. In children, blood pressure measured by the oscillometric device was poorly correlated and had wide limits of agreements with the sphygmomanometer. Furthermore, the oscillometric devices overestimated systolic blood pressure in children with higher readings. The applicability of automated blood pressure measuring devices in children has limitations and cannot be recommended. © 2008, European Society of Cardiology. All rights reserved.