This volume contains not only papers which were presented at the workshop held at the University of Kiel, Germany, on the "Importance of Physical Factors in Arid Ecosystems Research”, but also projects in progress or referred to at the meeting and which have since come to fruition. The papers fall into four main categories - soils, soil organisms, vegetation, and ecology. Many of the papers reflect research carried out in the Negev desert of Israel within the experimental stations of the AERC - Avdat, Nizzana and Sede Boker; others were undertaken in east Sahara. On the subject of soils, Blume et al. describe soil formation and ecology of sand dunes. Alaily and Pohlmann analyzed the structure of extremely arid soilscapes using Landsat data. Amit and Harrison studied the influence of biogenic processes on calcic soil formation. Singer highlighted similarities and differences in the soil mineralogy of hot and cold deserts. The role of animals in desert ecosystems is reflected in the papers of Steinberger and Shachak et al., whereas the role of microbes was studied by Yechieli et al. Holzapfel et al. examined the effect of site conditions on vegetation in a desert environment, while El-Kady et al. investigated the influence of landuse on vegetation. Pollination of desert plants was studied by Küchmeister et al. and by Wolf and Shmida. Schreiber et al. synthesized many years of integrated interdisciplinary research in desert ecology. We trust that this volume will be of interest to those working in geo-ecology.