The placenta operates as a vital interface between the mother and fetus. In addition to facilitating fetal nourishment, it acts as a barrier both to potentially deleterious agents and to contact between their two immune systems. As a consequence, damage to the placenta, even on a relatively small scale, could be very dangerous to the fetus. Therefore, wound repair mechanisms are likely to be of great importance in ensuring that an intact placental barrier is re-established as soon as possible. By use of an in vitro method for injuring and subsequently culturing small pieces of first trimester villous tissue, we have observed a number of indications that a wound response is initiated. Pronounced expression of transforming growth factor-beta1, heavy infiltration of macrophages and late deposition of tenascin in the region of the wound all provide good evidence of some form of healing activity. Furthermore, we have noted that these indicators are suggestive of 'adult-type' rather than 'fetal-type' repair processes.