Background: Heart rate variability (HRV) is an indicator of autonomic activity in the regulation of circulation and changes have been associated with several pathological conditions. Aims: The aim of the study was to acess the HRV as a predictor of extubation failure in pediatrics. Methods: In this prospective observational pilot study, we included all consecutive patients from 1 month to 18 years of age who were admitted to the PICU in the ICr-HCFMUSP, São Paulo - Brazil. They were submitted to the spontaneous breathing test (SBT) and evaluated by HRV by the time and frequency domain variables derived from the Polar V800 equipment and the Kubios HRV Standart® program. Results: A total of 36 patients [age 17 (2-216) months; male/female: 20/16; PIM2 3.9 (0.3-45.5); CRP (C-reactive protein) 20.2 (0.1-327); time of mechanical ventilation 5.0 (1.0-64.0) days] were included the study. The main diagnoses were 17 patients with lung diseases, 06 liver diseases, 08 neurological diseases, 03 sepsis/ septic shock, 01 nephropatic and 01 gastric disease. The data analyzed on HRV described in Table 3. Conclusions: From the data analyzed, it can be concluded that the analysis of heart rate variability was not a predictor of success/failure of tracheal extubation for the pediatric sample studied.