Background: Over the last two decades use of ultrasonic shears has grown in complex surgery where both precise dissection and meticulous hemostasis is required. With the introduction of HARMONIC® HD 1000i Shears (HD1000i), surgeons can now depend upon a single instrument to perform minimally-invasive dissection while securely sealing vessels up to and including 7 mm in diameter. This study was performed to compare HD1000i to the previous version of the device (HAR7) in sealing, dissecting and adhesion formation.