This study investigated the clinical relevance of early general chest ultrasonography (ie, heart and lung recordings) in patients in the ICU with acute respiratory failure (ARF).We prospectively compared this diagnostic approach (ultrasound) to a routine evaluation established from clinical, radiologic, and biologic data (standard). Subjects were patients consecutively admitted to the ICU of a university teaching hospital during a 1-year period. Inclusion criteria were age ≥ 18 years and the presence of severe ARF criteria to justify ICU admission. We compared the diagnostic approaches and the final diagnosis determined by a panel of experts.Seventy-eight patients were included (age, 70 ± 18 years; sex ratio, 1). Three patients given two or more simultaneous diagnoses were subsequently excluded. The ultrasound approach was more accurate than the standard approach (83% vs 63%, respectively; P < .02). Receiver operating characteristic curve analysis showed greater diagnostic performance of ultrasound in cases of pneumonia (standard, 0.74 ± 0.12; ultrasound, 0.87 ± 0.14; P < .02), acute hemodynamic pulmonary edema (standard, 0.79 ± 0.11; ultrasound, 0.93 ± 0.08; P < .007), decompensated COPD (standard, 0.8 ± 0.09; ultrasound, 0.92 ± 0.15; P < .05), and pulmonary embolism (standard, 0.65 ± 0.12; ultrasound, 0.81 ± 0.17; P < .04). Furthermore, we found that the use of ultrasound data could have significantly improved the initial treatment.The use of cardiothoracic ultrasound appears to be an attractive complementary diagnostic tool and seems able to contribute to an early therapeutic decision based on reproducible physiopathologic data.