The IS-ML model is a basic tool used in the teaching of short-term macroeconomics. Teaching is essentially done through the use of graphs. However, the way these graphs are traditionally taught does not allow the learner to easily visualise changes in the curves. The IS-LM simulation program overcomes difficulties encountered in understanding the curves used in the model because, through it, the students can visualise the changes in these curves when the model's parameter values are modified. The IS-LM simulation program is presented and the effectiveness of its application to a group of macroeconomics students at the University of Seville during the 2009/10 academic year is evaluated. Analysis of variance (ANOVA) of all students' scores and some complementary statistical tests were applied, distinguishing between students who used the simulator and those who did not. The average score obtained by the former in a model comprehension test was significantly higher than that of the latter. (Contains 4 tables and 4 figures.)