Alphai-antitrypsin is a major component of alpha-1-electrophoretic band of serum protein. Because alphai-antitrypsin is a broad spectrum inhibitor of proteolytic enzymes such as trypsin, elastase or collagenase, it is so called as Pi (Protease inhibitor) system. It is generally believed that the inhibition of granulocytic proteases by alphai-antitrypsin is most important for protecting the human organism against autodigestion. Alphai-antitrypsin is under genetic control, and more than 30 codominant variant alleles at a single chromosomal locus have been identified. Some of these alleles (particularly the alleles z, s, null) have been associated with serum alphai- antitrypsin deficiency of varying degree and with pulmonary emphysema or juvenile liver cirrhosis by autodigestion of normal tissue. We determined Pi phenotypes by IEF (isoelectric focusing) method in 440 normal controls and 143 patient of liver cirrhosis probably at first in Korea. Our purposes were determination of the distribution of Pi phenotypes in Korea and the clinical significance of Pi phenotypes in liver cirrhosis patients. The results as follows; 1) The Pi gene frequencies of 440 normal population are M1 = 0.7447, M2 = 0.1682 M3 = 0.0761, M4 = 0.0046, I=0.0023, S =0.0011, G=0.0034 (p>0.10). 2) The Pi gene frequencies of 143 liver cirrhosis patients (male 97, female 46) are M1 = 0.7443, M2 = O.Zll63 M3=0.0489, P=0.0070, Z=0.0035, (p>0.70) and alphai-antitrypsin deficiency case was seen only one patient. 3) There was no significant difference between normal population and liver cirrhosis patients in Pi gene frequency (p>0.20). Therefore, in Korea, there was almost no clinical signinficance of alphai- antitrypsin deficiency in old age liver cirrhosis except Juvenile cirrhosis.