The teaching of complex knowledge domains should not be restricted to linear explanations but instead should allow the learner to travel through domains along different routes. Simulation programs provide a microworld in which the user has the freedom to explore the embedded concepts and relations by manipulating parameters and studying the resulting changes in the simulation environment. In this study two experiments were conducted to investigate the educational value of a simulation program modelling the relations between erosion and agriculture in a developing country as part of the secondary school geography curriculum. The hypothesis tested was that studying the complex domain through exploration with a simulation program decreases the retention of facts and concepts but increases performance on a problem solving test, compared with studying the same domain through traditional classroom explanation. The first experiment showed that the exploration group outperformed the explanation group on both factual knowledge and problem solving questions. A second experiment was run to control instruction time for both groups and to add a demonstration of the simulation program to the explanation condition. Under these conditions there were no post-test differences between the explanation and the exploration group. It is hypothesized that training in how to use a simulation environment to study a domain is necessary to take full advantage of the facilities to explore the domain.