Purpose: To study the acute and chronic tissue effects of using high pressure CO2 to dissect tissues during laparoscopic procedures. Materials and Methods: A 5-mm. laparoscopic pneumodissector, capable of delivering brief bursts of high pressure CO2 (20 to 100 psi), was discharged on a variety of porcine tissues including the renal hilum. Acute and chronic histological sections, intraoperative blood gases and perioperative renal scans were obtained. Results: The only tissue with significant acute damage was the spleen. Acute changes in other tissues were minimal; long-term studies revealed no discernible damage to these same tissues. Intraoperative blood gases revealed no significant changes in the serum pCO2 or pH. Likewise, there was no renal damage discernible by renal scans. Conclusions: Pneumodissection at 50 psi is a safe method for dissecting the porcine kidney and the vessels of the renal hilum. Clinical studies are pending.