This paper reviews the interest of using context for participative simulation in virtual environment for training. Our aim is to simulate some cognitive mechanisms in order to obtain credible agent's decision-making. Another interesting aspect is the explanation needed when the learner makes a mistake. We argue, in this article, that context is a good concept to give better explanations. We describe a case-based reasoning architecture using a high level description of context. The situation's context is divided in social, environmental, historical and personal contexts. We introduced a context representation to use with a case-based reasoning system. At last we show an example of an agent decision-making.