The activity of phospholipase A2 (PLA2) and the content of prostaglandins (PGF and PGE-A) in swine blastocysts were determined on Days 7 through 14 of gestation by using radioenzymatic and radioimmunoassay techniques. Both PLA2 activity and PG content increased in the blastocyst with age. PLA2 activity on Day 14 and PG content on Day 12 were significantly higher than those on earlier stages of pregnancy. The content of PGE-A was always greater than that of PGF and the difference became significant on Days 11 and 12 of pregnancy. It is suggested that PGs of embryonic origin may be associated with blastocyts elongation and migration as well as early pregnancy recognition in the pig.