This study was conducted to estimate the correlation coefficient between pig weights by breeze, parity, furrowing season, duration of pregnancy and sea on the basis of the data obtained from total 2.498 pigs of Landrace, Berkshire and Yorkshire born from 1982 to 1983 at the livestock station, Gyeongsang Nam-do. The data were analyzed by the SPSS package program(Nie, 1975) and Miller`s method C 1983) and the results obtained were as follows: In correlation coefficients between pig weights by breed, the correlation coefficients between pig weight, at birth(PWB) and pig weight at 21 days(PW21) in Berkshire were significantly (p$lt;.05) higher than these in Yorkshire and PW21 in Berkshire seemed to increase more as PWB was heavier. though the correlation coefficient between PW21 and Pig weight at 56days(PW56) was not significantly different (P$lt;.05) between breeds, PW21 was more correlated with PW56 than PWB. In correlation coefficients between pig weighte by parity, the correlation coefficient between P1V13 and PW21 was significant different (p$lt;.05) between 7th parity and 1, 4, 5, and 8th parity groups, specially the correlation coefficient between PWB and PW21 in the 7th parity group was .5118, and there was the high correlation between PWB and PW21. The correlation coefficient between PW21 and PW56 was high in the other groups except the first parity and PW56 in parity seemed to increase more as PW21 was heavier. In correlation coefficients between pig weights by furrowing season, though the correlation coefficients between PWB and PW21 and PW56 were nonsignificant differences (p$lt;.051), the correlation coefficient between PW21 and PW56 was significantly (p$lt;.05) higher in the fall and winter-born groups than in the spring and summer born groups. In correlation coefficients between pig weights by duration of pregnancy, the correlation coefficient between PWB and PW21 was significantly different (p$lt;.05) between the 110 days group and the 111 days group and was not significant (p$lt;.05) between the other groups. The correlation coefficient between PWB and PW56 was significantly (p$lt;.05) higher with .6840 and .5935 in the 111 days and 119 days groups than in the other groups, and the correlation coefficient between PW21 and PW56 was significant differences (p$lt;.05) between the 112 days group and the 110 days groups. The correlation coefficient in the 112 days group was the highest with .7275. In correlation coefficients between pig weights by sex, the correlation coefficients between PWB and PW21 and PW56 were significantly (p$lt;.05) higher in the male group than in the female group. Specially, PW21 was more correlated with PW56 than PWB. From the results summarized as above, it could be inferred that PWB be more correlated with PW21 than PW56, and PW56 seem to increase more as PW21 was heavier because there was the more correlation between PW21 and PW56.