The phenotypes, genotypes and its gene frequency in genetic variant of Transferrin (Tf) and Pre-albumin (Pa) in serum proteins from total 134 individual pigs, Large White (LW), Duroc (D), Berkshire (B), Landrare (L) and Crossbred (C.B), reared in Korea were investigated by means of starch gel electrophoresis and their gene frequencies and genetic similarities were compared with those of foreign Pig breeds. The results are summarized as follows: 1. Tf and Pa of serum protein in pigs were controlled by co-dominant autosomal allelic gene of TF^A and Tf^B, and Pa^A and Pa^B, respectively. 2. In the phenotypes of Tf of LW, B, L and C.B breeds, Tf AB and Tf BB genetic variants were observed. In the D breed only Tf BB variant was found and the Tf AA homozygous was not observed in all breeds. In the phenotypes of Pa, genetic variants of Pa AA, Pa AB and Pa BB were commonly observed in all breeds. However, one pig of Tf AB heterozygous was appeared in the L breed. It was supposed to crossbred pig because of including A gene. Therefore, it was considered that the purity of a boar and a breed sow in Korea was in need of reexamination. Distribution of the phenotypes of serum protein loci in all the breeds with the exception of C.B breed agrees with Hardy - Weinberg equilibrium. 3. The gene frequencies of Tf B in LW, B, L, D and C.B breeds were 0.714, 0.833, 0.917, 1.000 and 0.160, respectively. In the Pa the LW, D and B breeds showed high gene frequency of the Pa^A variant with 0.571, 0.625 and 0.667, but Pa^B variant showed low gene frequency with 0.429, 0.375 and 0.333, respectively. However, Pa^B with a frequency of 0.583 was slightly higher than that of Pa^A (0.417) in the L breed. Frequencies of 0.571, 0.625 and 0.667 for the LW, D and B breeds showed high gene frequency of the Pa^A, whereas Pa^B showed low gene frequency (0.429, 0.375 and 0.333, respectively). The Pa^B with 0.604 gene frequency in C.B breed was also high, but Pa^A was in low gene frequency of 0.396.