A model for chronic perfusion of the liver of ruminants was developed. This allowed for investigation of the pathophysiology of pyrrolizidine alkaloids (PA) in two species. This model has general application to toxicological studies for both acute or chronic perfusion, as well as, metabolic studies utilizing sheep, cattle or goats. Catheterization of the portal vein via the right ruminal vein was done to separate the ruminal effects of toxin metabolism and absorption from the direct effects of PA on liver tissue. The selection of this vessel insured the equal distribution of infused substances throughout all lobes of the liver. A left flank laparotomy surgical approach was used. A dacron patch glued to the catheter at vein entry site eliminated a number of common catheter problems. Catheters were used for infusion of up to 2 L/daily for 20 d to 7 mo.