Objective: To present an unpublished reason for an arrhythmic electrocardiogram (ECG) recording during kangaroo care in a preterm infant. Design: Case report. Patient: Preterm infant. Measurements and main results: A preterm infant exhibited cardiac arrhythmia on the ECG monitor during kangaroo care, leading to interruption of kangarooing. Arrhythmia disappeared after placing the baby back into the incubator. The most likely reasons for arrhythmia were excluded. However, arrhythmia reappeared upon continuation of kangaroo care. ECG monitoring revealed the reason for the monitoring error. Conclusions: ECG monitoring during kangaroo care should cause error because of superimposed electric activity from the parent. Oxygen saturation represents a more reliable method of monitoring during kangaroo care. (Pediatr Crit Care Med 2004; 5:455-456)