In contrast to an increasing number of agent-based applica-
tions in various domains, there has been very little work on
maintenance and evolution of agent systems. This paper ad-
dresses this gap with a focus on change impact analysis, i.e.
estimating the potential eects of changes before they are
made as an agent system evolves. We propose a technique
for performing impact analysis in an agent system using dy-
namic information about agent behaviour. Our approach
builds a representation of an agent's behaviour by analyzing
its execution traces which consist of goals and plans, and
uses this representation to estimate impacts.