Over the last decade the use of numerical techniques for the solution of the problems of physics, engineering, chemistry, biology and the social sciences has increased by leaps and bounds, and it was felt that the time was ripe for holding a Discussion Meeting on some topic in numerical analysis. This was intended not merely to provide an opportunity for experts in the field to get together, since there are many specialized meetings in numerical analysis these days. The aim was rather to give scientists in general who are interested in numerical methods a chance to find out what is being done, so that they can make greater use of this work and hopefully influence its future development. After some deliberation I decided on partial differential equations as the topic, in spite of the fact that it is not an area in which I have made any direct contribution in recent years. This is because I believe it to be one of the most important and challenging fields; indeed the solution of systems of p. d. es lies at the very heart of the problems of applied mathematics. Long after we have the more basic fields of linear and nonlinear algebra and approximation theory in good order the problems arising in the solution of p. d. es will still be with us. The work that has been done in numerical analysis may then appear as a preliminary sharpening up of the tools we are to use.