Rib fractures are the most common (25%) injuries resulting from blunt chest trauma, and are usually revealed on radiographs. Radiography sometimes cannot show fractures, especially those in costal cartilages, except for densely calcified ones. Several authors have recently investigated the role of ultrasound in the detection of rib fractures. We conducted this study to investigate possible rib fractures with ultrasound, determine those overlooked on chest x-ray, and analyze the possible clinical predictors of these insidious rib fractures in minor or mild blunt chest trauma. A total of 20 patients with minor mild blunt chest trauma were enrolled into this study. All radiographs were reviewed by two radiologists who noted rib fractures or other complications. Ultrasonography was performed in the radiology department using a linear transducer by one radiologist. The costal cartilage normally appears relatively hypoechoic compared with the osseous rib. Fractures of the rib, costochondral junction, and costal cartilage were denoted by a clear disruption of the anterior echogenic margin. A total of 20 patients with normal radiological findings, but continuing symptoms were evaluated by ultrasound. The most common etiology of trauma was a fall, as seen in 60% of the patients. None of the rib fractures were identified radiographically. Sonography detected 26 rib fractures in 18 of 20 subjects at presentation. Sonography reveals more fractures than radiography and will reveal fractures in most patients presenting with suspected rib fracture.