It is accepted that colostral macrophages have protective effects on gastrointestinal tract of the neonates. Macrophages act as a major defensive cells in colostrum and serve as a main source of colostral prostaglandins which are known to exert cytoprotection for gastrointestinal tract of neonates against infectious agents and drugs such as aspirin. This study was conducted to evaluate the total cell numbers and differential counts for macrophages, neutrophils and lymphocytes in colostrum of Korean mothers. To compare the level of PGE2, 6-keto-PGF1$alpha$, and TXB2 between colostrum and serum of postpartum mothers, radioimmunoassay adopting eicosanoids-antibody complex method was applied instead of charcoal method. The results were as follows : 1) Total defensive cell count was 7.6$pm$2,37$ imes$106 cells/ml, differential counts of macrophages, neutrophils and lymphocytes were 57.49$pm$4.14%, 37.98$pm$4.43% and 4.29$pm$0.73% respectively. 2) The order of prostaglandin level in colostrum which are known to enhance development and cytoprotection of gastrointestinal tract, was 6-keto-PGF1$alpha$, TXB2 and PGE2. Colostral PGE2 level was 584.6$pm$72.3 pg/ml, higher than that of serum(p<0.01). 6-keto-PGF1$alpha$, the most abundant prostaglandin in colostrum was higher than in serum level, too (p<0.01). Serum TXB2 level of postpartum mothers(n=42) was higher nine times than that of colostrum(p<0.01), which seems to cause vasoconstriction of uterus in postpartum period. 3) In preterm mothers, serum level of TXB2 level in both groups.