In March 23rd 1986, a small group of scientists from 11 countries met at the Department of Limnology, University of Vienna, to discuss sediment phosphorus problems. The discussions lasted three days during which twenty lectures were delivered and discussed under the following headings: 1. Sedimentation, 2. Release, 3. Bioavailability and 4. Fractionation of P. The final day was devoted to summarize the information gathered and to make proposals for future research. Four working groups were formed for this task. In the first group (Sedimentation) the sources, transport and transformation processes of particulate phosphorus during sedimentation were discussed. The second group (Release) was dealing with concepts, causes and consequences of phosphorus fluxes through the interface. Group number three (Bioavailability) treated the availability of different P compounds to organisms, and group four (Fractionation) tried to summarize and to update the present knowledge of fractionation methods. Some of the original papers presented at the meeting appear in this volume; working group summaries and recommendations are located at the end. The intention was not to present a detailed treatise on the phosphorus dynamics but rather an overview of the current knowledge, the state of the art and to list the topics which should be tackled intensively in the near future. At the end of the workshop the participants generally agreed that a better understanding of P dynamics in the sediment-water interface needs research in all the discussed topics viz. sedimentation, release, bioavailability, fractionation. As the outcome of the workshop was encouraging, a follow-up meeting is planned for 1988 in Sweden.