Resumen: Introduction: In pediatrics, it is decisive to assess the severity of bronchial obstruction; to this end, different clinical scoring scales have been developed, including the modified Tal score. The objective of this study was to determine its validity and reliability in children seen at two emergency departments of Concepción, Chile. Population and methods: Prospective, cohort study. Children younger than 36 months old diagnosed with bronchitis and/or bronchiolitis during the winter and spring months of 2015 were included. Concurrent criterion validity was determined based on the correlation between the score and oxygen saturation, as a reference standard. Predictive validity was assessed based on the association between the score and the probability of a new visit to the emergency department in the following 7 days. The area under the ROC curve was estimated. Reliability between kinesiologists and physicians was established based on the intraclass correlation coefficient (ICC). A p value < 0.05 was considered statistically significant. Results: A total of 102 children were assessed; a weak correlation between the score and oxygen saturation was observed among kinesiologists (Rho = -0.41). An association was observed between the score and the probability of a new visit to the emergency department. The area under the curve measured by both health care providers was > 0.80. Inter-observer reliability between physicians and kinesiologists showed a weak correlation (ICC = 0.17). Conclusions: The modified Tal score shows an adequate predictive validity, but a poor validity when correlated to oxygen saturation, and a weak inter-observer reliability.