The number of Carterocephalus palaemon has decreased drastically both in the Netherlands and in Great Britain. In England, where the species has not been seen since 1975, a reintroduction is under consideration. Knowledge of ecology is essential and for this reason a study has been made in the Netherlands on the biotope requirements of this butterfly species. C. palaemon occurs mainly in moist, rugged grasslands and clearings in woods. Its hostplant is Calamagrostis canescens or Molinea caerulea. After many investigations the ideal structure of the habitat can be made and management advice be given accordingly. Furthermore the situation in the Netherlands is of importance as an example for the rcintroduction in England.