Purpose : To evaluate the effectiveness and safety of a new liquid embolic material, Embol-78-12, in portalvein embolization (PVE) in pigs. Materials and Methods : A total of 13 pigs were used in this study. The testmaterial, Embol-78-12, was obtained by hydrolysis of polyvinyl acetate (PVAc) and dissolved in a mixture of 45%ethanol and 55% nonionic water-soluble contrast medium (Ultravist 370) (v/v). Its radioopacity was good. PVEinvolved the use of 5cc of Embol-78-12 in the left lobe (left and left paramedian segments) of the liver ; toprevent reflux of the embolic material through the percutaneous transhepatic route, an oclusion balloon catheterwas used. Six pigs were sacrified immediately after PVE and formed a normal control group, used to determine theaverage volume ratio of the right and left lobe of the pig. Follow up study was performed in the other seven pigs; changes in body temperature and liver function test (GOT, GPT, and total bilirubin) at 0, 3, 6, 10, 14 daysafter PVE were recorded. Four pigs were sacrificed at 2 weeks, and three at 4 weeks. The embolization rate,changes in the volume ratio of the right and left lobe, the atrophy ratio of the embolized lobe and regenerationrate of the non-embolized lobe were evaluated. Results : In the left lobe, PVE was successfully completed in allpigs. Follow-up study revealed evidence of increased body temperature in only one of six pigs and virtually nochange in GOT, GPT, and bilirubin levels. In the control group, average liver volume was 511+43 cm3 ; volumepercentage of the right and left lobe of the liver was 55+2% and 45+1, respectively. The embolization rate in thisstudy was 45+1%. When the animals were sacrificed at 2 and 4 weeks, embolized left portal vein showed completeocclusion. Volume percentage of the right and left lobe of the liver was 71+3 and 29+3 at 2 weeks, and 84+3 and16+3% at 4 weeks. The atrophy ratio of the embolized lobe was 22% at 2 weeks (average decrease : 51cm3) and 49% at4 weeks (average decrease : 114 cm3). The regeneration rate of non-embolized lobe was 12.6 cm3/day (176 cm3 for 2weeks) during the first 2 weeks and 8.9 cm3/day (125 cm3 for 2 weeks) during the next 2 weeks. Conclusion : Innormal pig liver, embol-78-12 used with occlusion balloon catheter is an effective and safe material for PVE. Webelive it is suitable for PVE in the clinical field and will be used in many clinical applications in the field ofinterventional radiology.