PURPOSE: To describe the role of ultrasound biomicroscopy in the detection and localization of foreign bodies in anterior ocular segment foreign body after trauma. METHODS: In a prospective study, ultrasound biomicroscopy was performed in five eyes of five consecutive patients with suspected anterior ocular segment foreign body. RESULTS: In all five eyes, ultrasound biomicroscopy detected and precisely localized small foreign bodies (metallic in two eyes, stone in one eye, plastic in one eye, and ceramic in one eye) in the cornea (one eye), superficial sclera (one eye), and anterior ocular segment (three eyes). Operative procedures to remove the intraocular foreign bodies (three cases) were guided by the ultrasound biomicroscopy information. CONCLUSIONS: Ultrasound biomicroscopy is a noninvasive method for detecting anterior segment intraocular foreign bodies after perforating trauma. It can be used to accurately diagnose foreign bodies and assist in surgical management, particularly when direct visualization is obscured because of the trauma. In eyes with partial-thickness corneoscleral lacerations or sealed full-thickness corneoscleral laceration and suspected anterior ocular segment foreign body, ultrasound biomicroscopy is a safe and effective method for detecting and localizing foreign bodies in the anterior ocular segment.