Background and Aim: Bronchiolitis is an acute viral lower respiratory tract infection. It is a common disease among children below 2 years old, resulting in frequent presentation to the emergency department and occasionally admission1 . For proper management of such patients, studying the disease spectrum and the risk factors is important2 . The aim of this study was to investigate the demographics and risk factors for severe bronchiolitis in children (0–2 years old), in the emergency department (ED) at Sultan Qaboos University Hospital (SQUH). Methods: We conducted a retrospective cohort study, including children ( < 2 years old), who came to the ED with a presentation suggestive of bronchiolitis. We reviewed the charts for a two-year period (January 2015–December 2016). Demographic and baseline characteristics were gathered from electronic medical records and then analyzed. We categorized patients into severe and non-severe bronchiolitis according to the guidelines set by the New South Wales (NSW) Ministry of Health in Australia in 2012 for the “Acute Management of Bronchiolitis in Infants and Children”3 . Therefore, in our study children who were considered to have severe bronchiolitis had one of the following: unwell appearance, apneas, severe tachypnea (>70 breaths/min), bradypnea ( < 30 breaths/min), moderate to severe grunting, cyanosis, pallor, oxygen saturation < 90% in air (or < 92% in O2), tachycardia (>180 beats/min) and difficulty in feeding (taking less than 50% of normal feed).We investigated the following risk factors to predict severe bronchiolitis: maternal age, birth weight, prematurity ( < 37 weeks of gestational age), age < 12 weeks, congenital heart defects, congenital respiratory diseases, immunodeficiency, and global developmental delay. We described the cohort using descriptive statistics and performed a logistic regression analysis to determine the risk factors for severe bronchiolitis. Results: Of the 235 children with bronchiolitis, 133 had severe bronchiolitis while 102 had the non-severe form of the disease, with a greater percentage of males than females in both groups. The majority of children with severe bronchiolitis were in the age < 3 months group (32%), while the least was in the ≥ 12 months age group (10%). There was a trend toward statistically significant results for the following factors: chronological age < 12 weeks (OR = 2.67, 95% CI = 0.89–2.67), congenital cardiac diseases (OR = 2.12, 95% CI = 0.85–5.30) and congenital respiratory diseases (OR = 1.86, 95% CI = 0.80–4.27).The following factors were associated with severe bronchiolitis using stepwise logistic regression: increased heart rate (OR = 1.046, 95% CI = 1.026 – 1.066), decreased SpO2 (OR = 0.890, 95% CI = 0.827 - 0.957), male gender (OR = 2.248, 95% CI = 1.105 – 4.573), irritability (OR = 2.209, 95% CI = 1.024 – 4.769) and global developmental delay (OR = 3.5, 95% CI = 1.0 – 12.537). Conclusion: Multiple factors were associated with severe bronchiolitis and three were trending toward significant association inc...