In order to study developmental and metabolic characteristics of normal and abnormal placental tissue, especially purine metabolism and effects of oxygen deprivation, we have optimized a method for primary culture of trophoblastic cells. After collagenase dispersion, the cells were enriched by filtration and cultured in Ham's F-10 medium. The cell population contained mainly syncytiotrophoblasts (over 90%), characterized using anti-cytokeratin and -vimentin antibodies, and the viability remained over 90%. The plating efficiency was significantly higher on dishes coated with fibronectin, collagen-IV or laminin, when compared to uncoated dishes. On the former, a higher degree of specialized function was retained, as evidenced by consistently higher chorionic gonadotropin (hCG) secretion. Comparing first trimester and term trophoblast, the following observations have been made: no growth of either first or third trimester syncytiotrophoblast in primary culture; active mesenchymal cell growth in first trimester, but none in term cultures; hCG and pregnancy-specific beta-1-glycoprotein secretion inversely proportional to gestational age; a six-fold increase in alkaline phosphatase, but a 40% decrease in 5-nucleotidase activity with increasing gestational age, but no difference inthe activities of three other key enzymes of purine catabolism and reutilization; active de novo purine synthesis, but a large inter-placental variation. In conclusion, the trophoblastlc character and specialized function in the primary cultures are retained,and they can be used for studies on normal and abnormal placental metabolism.