Previously, this group reported on a system of extrauterine incubation of a goat fetus, in which the fetus is surrounded by artificial amniotic fluid and connected to the circuit with an ECMO (extracorporeal membrane oxygenator) by the umbilical arteries and veins. The following is a summary of recent progress using an improved method of catheterization and a new system that included a dialyzer within the circuit. Nine goat fetuses were used in this experiment. Six goats were successfully incubated; the duration of their incubation was 146.5 +/- 61.3 h (mean +/- SD). The longest one was 236 h. Slowly progressive circulatory depression was thought to be the main cause of fetal death. Marked tendencies to bleeding and water retention were not observed in any cases. Stable serum electrolyte levels were maintained.