Strangulation obstruction was induced in anesthetized ponies for periods of 2 and 3 hours by clamping 45-cm segments of jejunum and their veins only (venous strangulation obstruction, VSO) and arteries and veins (arterial and venous strangulation obstruction, AVSO). These types of strangulation obstruction were studied in 4 segments in each of 4 ponies allowed to survive 12 hours (group 1) and in a single segment in each of 10 ponies allowed to survive 42 days (group 2) after the strangulation period ended. On visual inspection, segments subjected to VSO had hemorrhage and edema in the bowel wall and mesentery and were dark purple after all time intervals. They improved slowly after clamps were removed, but remained hemorrhagic and edematous. Segments subjected to AVSO were purple and had mild edema and scattered petechiae in the bowel wall and mesentery. They improved rapidly and closely resembled normal bowel after 5 minutes of reperfusion. On light and scanning electron microscopy, the mucosa of intestine subjected to VSO and AVSO had necrotic, denuded villi 1 hour after the strangulation periods ended. Twelve hours after removal of occlusion devices in group-1 ponies, 4 (25%) segments were unchanged, 4 (25%) had deteriorated, and 8 (50%) had stunted villus remnants partly or completely lined with regenerating epithelium. Separation and detachment of villus tip mucosal cells were seen in 3 of 4 control segments, 1 and 12 hours after the strangulation periods ended.(ABSTRACT TRUNCATED AT 250 WORDS)