Agents are semi-intelligent programs that assist the user in performing repetitive and timeconsuming tasks. Information discovery and information filtering are suitable domains for applying agent technology. Ideas drawn from the field of autonomous agents and artificial life are combined in the creation of an evolving ecosystem composed of competing and cooperating agents. This study analyzes co-evolution model of information-filtering agents that adapt to the various user's interests, and information discovery agents that monitor and adapt to the various on-line information sources. Results from a number of experiments are presented and discussed.