PURPOSE: To demonstrate the usefulness of ultrasound biomicroscopy (UBM) in detecting and localizing small ocular foreign bodies. METHODS: This is a retrospective study of the records of 555 consecutive patients evaluated by UBM by the Visual Physiology Unit of the Wills Eye Hospital from August 1994 to November 1997. RESULTS: In 9 patients, a foreign body was identified. In 6 patients, the history suggested the presence of a foreign body, but one could not be detected by clinical examination. In 2 patients, the referring physicians requested UBM to determine whether or how deep a known foreign body had penetrated the globe. In 1 patient, the foreign body was not suspected clinically. In regard to other diagnostic techniques, CT failed to identify the foreign body in 1 patient. In another, contact B-scan ultrasonography failed. In a third, both CT and contact B-scan ultrasonography failed. The foreign body was intracorneal in 2 eyes, subconjunctival in 2, intrascleral in 3, and intraocular in 2. Six were nonmetallic. Two were metallic. In one case, the foreign body was lost and its composition is unknown. In 5 cases, the UBM findings altered the patient's management. CONCLUSIONS: UBM is a valuable adjunct in the evaluation of small, anteriorly located foreign body that may not be detectable by other methods. UBM may be especially useful for finding nonmetallic foreign bodies.