This study was conducted to investigate the diagnostic value of a new sonographic technique for the detection of intraabdominal free air. Seventy-two patients with a suspected gastrointestinal tract perforation were included in the study and prospectively evaluated by sonography and abdominal and chest radiography for the detection of intraperitoneal free air. A new sonographic technique (the scissors maneuver) was used to detect intraperitoneal free air superficial to the liver; the maneuver consists of applying and then releasing slight pressure onto the abdominal wall with the caudal part of a parasagittaly oriented linear-array probe. The results of the imaging studies were correlated with surgical findings when possible. Sixteen patients had a surgically proven gastrointestinal tract perforation causing pneumoperitoneum. Sonography and radiography each showed pneumoperitoneum in 15 patients, with 1 false-negative result for each modality. The sensitivity and specificity values of sonography and radiography were identical; sensitivity was 94% and specificity was 100% for both imaging modalities. The scissors maneuver was positive in all patients with sonographically detected pneumoperitoneum. Sonography is an effective tool in the diagnosis of pneumoperitoneum, with sensitivity and specificity equal to those of radiography. The scissors maneuver may be a useful adjunct for improving the diagnostic yield of sonography. Copyright 2004 Wiley Periodicals, Inc.