Continuous tissue expansion utilizing a continuous infusion device that maintains a constant expander pressure was previously demonstrated to be feasible and successful in obtaining rapid tissue expansion in a canine model. Intraoperative tissue expansion has been described and has gained some clinical acceptance as a method to gain rapid expansion. We compared the efficacy of continuous tissue expansion versus intraoperative tissue expansion in a piglet model. After completing a pilot study, continuous tissue expansion was performed in six pigs (14.5 to 20 kg) on one flank over a 3-day period utilizing an improved prototype device; at the termination of continuous tissue expansion, intraoperative tissue expansion was performed on the opposite flank. There were no complications or continuous tissue expansion device malfunctions. Intraoperative tissue expansion gave a true gain in area of 7.4 percent, while continuous tissue expansion produced a 22 percent gain (p < 0.02). When the effects of both recruitment and expansion were added, continuous tissue expansion gave a dividend of 286 percent versus 192 percent for intraoperative tissue expansion (p < 0.01). Biomechanically, intraoperative tissue expansion skin showed few differences from unexpanded skin, while continuous tissue expansion skin showed a significant increase in stress relaxation (47.78 versus 38.74) and decrease in breaking strength. Histologic analysis revealed some epidermal hyperplasia and inflammation surrounding the continuous tissue expansion expander and some vascular congestion over the intraoperative tissue expansion expander. We conclude that continuous tissue expansion is superior to intraoperative tissue expansion and that the prototype device may be useful clinically.