The effect of distal small bowel resection (DSBR) and/or ursodeoxycholic-acid (UDCA) ingestion on hepatic activities of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase and acyl-CoA:cholesterol acyltransferase (ACAT) was studied in rats. The total activity and the activity state of the enzyme HMG-CoA reductase were also determined. DSBR significantly increased the total activity of HMG-CoA reductase. This increase was enhanced when rats were treated with UDCA. The active form of the enzyme was increased by DSBR. However, the ingestion of UDCA did not modify these results. Therefore, the observed increase in the total activity of HMG-CoA reductase in resected-rats after the administration of UDCA was due to an increase in the inactive form of the enzyme. The activity of ACAT was decreased in resected animals. This decrease was greater after the treatment of UDCA in resected rats when compared with the corresponding group of untreated rats with UDCA. We conclude that UDCA ingestion increases the effect of intestinal resection on hepatic HMG-CoA reductase and ACAT activities.