Purpose: Propranolol is known to decrease portal pressure by reducing blood flow of portal vein. Per-rectal portal scintigraphy with Tc-99m pertechnetate has been introduced to evaluate the portal circulation and early diagnosis of liver cirrhosis. We evaluated the effects of propranolol on portal circulation by using per-rectal portal scintigraphy. Materials and Methods: We analyzed the portal hemodynamics by per-rectal portal scintigraphy in 51 patients with liver cirrhosis, 10 chronic hepatitis and 10 normal subjects. 38 patients with cirrhosis underwent per-rectal portal scintigraphy before and after propranolol medication. Per-rectal portal scintigraphy was performed after per-rectal administration of 370 MBq of Tc-99m pertechnetate. The shunt index was calculated as the ratio, expressed as a percentage of heart radioactivity to the sum of heart and liver radioactivity during the first 30 seconds. Results: The shunt index in 40 patients with cirrhosis (59.8¡¾27.2%) was significantly higher than that of normal control (5.0¡¾1.2%, p<0.01) and chronic hepatitis (11.4¡¾3.5%, p<0.01). Shunt index was significantly different according to Child's classification and the degree of esophageal varix (p<0.01). After propranolol medication, shunt index was significantly decreased from 59.9¡¾27.3% to 51.3¡¾15.3% (p<0.01) in 38 patients with liver cirrhosis. There was no significant difference of the amount of shunt index reduction after propranolol according to Childs' classification and the degree of esophgageal varix. Conclusion: The effect of propranolol on portal circulation was demonstrated as decreasing shunt index on per-rectal portal scintigraphy in patients with liver cirrhosis. Per-rectal portal scintigraphy may be useful to evaluate the portal circulation and to predict the effect of propranolol in patients with liver cirrhosis. (Korean J Nucl Med 1999;33:388-97)