There has been a significant progress concerning the development of networked virtual environments the past 20 years, and the gaming industry has recently been one of the most important actors. Earlier, the implementation of the network part was often a feature added to a game at a late stage of the design. This was to be changed when the pure network games emerged in the second half of the 90s. Games running over the Internet face different challenges compared to the ones managed by a single computer. Participants communicate by sending messages over the network, and since bandwidth is a limited resource, there must be developed techniques to keep this message traffic at the lowest level possible.This thesis addresses the problem of how to define the relevance between two clients in a massively-multiplayer-online-roleplaying-game (MMORPG). This is usually called relevance filtering. The goal is to minimize the collection of clients a certain participant has to communicate with at any given time during gameplay by defining an area of interest. This thesis suggests a two-stage relevance filtering: filtering in relation to the distance between two clients (their location in the virtual environment) and filtering concerning the level of interest between two clients. The former filtering technique is the main topic; a new idea is presented, and an implementation based upon this is described. Results achieved by simulation is then analyzed in order to discuss the use of the technique.