An ultrasound image in a 43-year-old man who presented with sudden onset of abdominal pain. The patient had a history of a duodenal ulcer and was aware of black stool prior to the presentation. On physical examination, he had diffuse abdominal tenderness with guarding. Bedside ultrasound was performed with the patient in the left lateral decubitus position. Reverberation artifacts on the ventral surface of the liver (arrows) indicated intraperitoneal free air. The artifacts were distinguished from other artifacts with respiratory movement (arrowheads), which originated at the lung surface