A series of animal models for portal hypertension was prepared using the method of portal vein constriction. Four New Zealand domestic rabbits and six dogs were given portal imaging by per-rectal administration of ⁹⁹mTc-MIBI and characteristics of quantitative portal hypertension were investigated. When the portal of domestic rabbits were constricted to 1/2, the heart/liver value (H/L) rose from 0.10±0.04 to 0.57±0.11, and the heart shunt index (S.I.h) rose from 0.08±0.03 to 0.36±0.09. These differences have significant meanings (p<0.05) . The shunt index for whole organs (S.I.w), however, only changed slightly. When the portal veins of the dogs were constricted to 1/3, 1/2 and 2/3 of their original widths, their H/L, S.I.h and S.I.w values rose in proportion respectively, and their correlation with the portal pressure measured during operation was very good. Immediately after the operation, the main feature observed was the compensational swelling of the spleen. One month later, image of the heart became even more conspicuous, demonstrating formation and establishment of the collateral circulation.