- Rationale: Estimates of the incidence of the Acute Respiratory Distress Syndrome (ARDS) in high and middle-income countries vary from 10.1 to 86.2 per 100,000 person-years in the general population. The epidemiology of ARDS has not been reported for a low-income country. The Berlin definition may not allow identification of ARDS in resource-constrained settings. Objectives: To estimate the incidence and outcomes of ARDS at a Rwandan referral hospital using the Kigali modification of the Berlin definition: without requirement for positive end expiratory pressure, hypoxia cutoff of SpO2/FiO2 ≤ 315, and lung ultrasound or chest radiograph for bilateral opacities. Methods: We screened every adult patient for hypoxia at a public hospital in Rwanda for six weeks. For every patient with hypoxia, we collected data on demographics and ARDS risk factors and performed lung ultrasonography. Measurements and main results: Fifty-one (4.9%) of 1046 hospital admissions met criteria for ARDS. Using various pre-specified cutoffs for the SpO2/FiO2 ratio resulted in almost identical hospital incidence values. Median age for patients with ARDS was 40 years, and infection was the most common risk factor (45.6%). Only 23.3% of patients with ARDS were admitted to an ICU; among all patients with ARDS, hospital mortality was 52.9%. Using traditional Berlin criteria, no patients would have met criteria for ARDS. Conclusions: ARDS is a common and fatal syndrome in a hospital in Rwanda, with few patients admitted to an ICU. The Berlin definition, while appropriate in high-income countries, underestimates the incidence of ARDS in low-income countries.