An adjustable, stainless-steel "ball and saddle" prosthesis has been devised for banding the main pulmonary artery in dogs. Comparisons were made between this prosthesis and circumferential cotton umbilical and Teflon tape banding in 20 dogs. The vessel lumen and pressure gradient across the banded area returned to normal after release of the ball and saddle band, but not after release of the circumferential tape bands. However, microscopic damage to the banded artery was noted in all dogs, with attenuation of the media being most evident in dogs with the steel ball and saddle prosthesis.