Sonographically guided fine-needle biopsy procedures are hampered by poor visibility of the needle tip. This study was performed to evaluate a new system for placing needles under sonographic guidance. The Biosponder needle (Advanced Technology Laboratories, Bothell, WA) incorporates a specialized stylet with a passive sensor at its tip. When an ultrasound pulse is detected by the sensor, an electrical signal is transmitted to the sonographic unit by a battery-powered electronic module connected to the stylet and to the scanner. This signal is converted into a bright, flashing marker on the screen at the precise location of the needle tip. The Biosponder system, which uses 20- or 22-gauge needles, was compared with a 20-gauge Turner needle (Cook, Bloomington, IN) in 18 patients with masses or fluid collections and two patients requiring nephrostomy tube placement. The tip of the Turner needle could not be localized precisely in any patient. The shaft of the Turner needle was seen clearly in 13 patients, poorly in three, and was not visualized at all in four patients. Excluding four instances of mechanical failure, the Biosponder system allowed precise localization of the needle tip in every patient and was consistently rated as easier to use than the Turner needle. We conclude that the Biosponder needle, with its precise tip localization and ease of use, is a valuable tool for sonographically guided needle placement.