To solve the problem of monitoring the patient during administration of anesthesia, a commercially available head-up display (HUD) was evaluated during one day of surgery at the Ohio State University Hospitals. This monitor is mounted on a headband worn by the anesthesiologist. It projects a monochrome image of monitor data directly into one eye. Eleven anesthesiologists tested the device. Most users were able to adjust to the monitor in about fifteen minutes. Nine of the testers expressed a desire to evaluate the monitor further. Their major complaints were that the connecting cable between the HUD and its computer was too short, the resolution of the monitor was inadequate, and the data on the screen were not organized in a familiar way. If these problems could be corrected, most users believed that this HUD could be a valuable tool to aid the anesthesiologist in the operating room.