Gastrointestinal motility and plasma PYY levels were investigated under chronic progressive large bowel obstruction in dogs. The obstruction device was applied arround the descending colon at a laparotomy and gastrointestinal motility was recorded with strain gauge force transducers in the conscious state. Complete obstruction occured at 26 days (21-33 days). The duration of postprandial interruption of motor complex (DIMC) in the antrum and duodenum were prolonged progressively, at partial obstruction (17.7±2.7 hr; p<0.05) and complete obstruction (23.O ± 4.0 hr: p<0.01) vs in control (13.7 ± 1.9 hr), while DIMC in the smal bowel showed no significant changes. Progressive obstruction caused hypermotility in the proximal colon to the obstrution and hypomotility in the distal colon. These dysmotility were improved after resection of the obstructed segment and anastomosis. Plasma PYY levels in the fasting state showed no significant increase at complete obstruction (42.6±14.5 pmol/l) vs in control (32.9±10.2 pmol/l)