This paper presents and discusses a number of criteria for the design and implementation of electronic market servers, It first briefly reviews a number of electronic markets currently operational over the internet then offers some ideas on the types of new markets that may become successful. It then presents the design criteria for market servers, necessary to support these virtual markets. Finally, it introduces the ECMarket server, an experimental server under development at Elecomm Corporation. This work emanates from the research conducted at McGill University and Euridis at Erasmus Universiteit during 1992 to 1995.