A new electronic device designed to detect glove holes, wet gowns and glove permeability was assessed during 50 general surgical operations. The cause of each alarm was recorded and the surgeon's awareness of any breach noted. Some 266 alarms were recorded of which 45 were ascribed to glove holes, 86 to wet gowns, 115 to glove porosity and 20 to other causes. Glove holes occurred in 29 of the 50 procedures; the surgeon was unaware of the hole in almost 70 per cent of cases. Holes were more common in laparotomy than in laparoscopic procedures (P = 0.006). In 20 per cent of instances surgeons did not respond immediately to the alarm (median delay 16 min). Six of eight surgeons who used the device indicated that they would do so regularly for major abdominal surgery. The electronic system accurately detects breaches in the surgeon-patient barrier. Its use should improve surgical discipline in acting to restore the barrier, protecting patient and surgeon alike.