This volume of the REU Technical Series (RTS 63) is the fourth on organic agriculture research in Europe. The first in this series are the proceedings of the expert consultation on Biological Farming in Europe, held in Basel from 30 September to 1 October 1990 (RTS 12), followed by a review of the status of Organic Farming Research in Europe in 1997 (RTS 54). The third volume on this topic (RTS 58) was the proceedings of the first workshop of the new Working Group on Organic Farming Research of the FAO Sustainable Rural Environment and Energy Network (SREN) held at the Research Institute of Organic Agriculture (FiBL) in Frick, Switzerland, 30 September to 3 October 1998.