Background: Soft tissue foreign bodies are a frequent cause of consultation in emergency rooms. It is difficult to verify their existence since conventional radiology only detects radio opaque objects. Ultrasound can be a useful diagnostic procedure. Aim: To report our experience in the detection of soft tissue foreign bodies by ultrasound examination. Patients and methods: The ultrasonographic appearance of vegetables, glass and plastic, metal, bone and stones was studied in gelatin preparations. In a second stage, 52 patients (27 male, aged 3 to 88 years old) were studied, in whom the presence of a soft tissue foreign body was confirmed surgically. Results: The mean error of the procedure for the assessment of foreign body size was 0.2 mm in vitro and 0.5 mm in vivo. The deepness and involved planes were correctly diagnosed in 96%, the number of fragments were diagnosed correctly in 94% of cases. The type of foreign body was identified correctly in 77% of cases and complications were detected in 100% of cases. Conclusions: Ultrasound is a sensitive and accurate method for the detection of soft tissue foreign bodies. (Rev Méd Chile 2000; 128: 419-424).