Over the past decade, the use of simulated experiments has grown to play a significant role in our undergraduate pharmacy and pharmacology experimental classes. These simulations, developed in-house, span a range of models from classical organ bath preparations, such as the guinea pig ileum, to models of in vivo preparations, the anaesthetised cat and pithed rat. Simulated experiments can be distinguished in terms of their complexity and the extent and realism with which they represent a particular experimental preparation or biological process. One particular theme has been the incorporation of quite simple simulations into tutorial packages, exemplified by the PharmaCALogy and PCCAL packages, developed in the 1990s. We have taken a different approach in producing self-contained simulations that are relatively complex, in terms of the drugs and experimental procedures that can be applied, allowing multiple drugs and concentrations to be added and interactions between drugs modelled. Real experiments are, of course, important in an undergraduate teaching program. If a student is to develop any real capacity in a field of research, they must engage with and develop practical skills in the experimental techniques of their discipline. However, our experience suggests that simulated experiments also have a distinct role to play in a physiological or pharmacological experimental teaching program. In particular, simulations permit a shift in the focus of activity, away from the performance of the experiment, towards experimental design and the analysis and interpretation of experimental data. Equally, if the primary aim of the experimental class is to provide an opportunity to actively explore the properties of a drug or physiological system, to support learning in a course or module, then the challenges of the real experiment may be an actual disadvantage. For example, our introductory pharmacology class which begins initially with real guinea pig ileum studies of classical agonist/antagonist actions, ends using an exact simulation of the same preparation which students use to perform an extended series of experiments, leading to the production of a short scientific paper on their results. Time constraints and the difficulties of acquiring large amounts of good quality data for large numbers of students, preclude this being achieved using real experiments. The simulation permits large amounts of data to be acquired faster than in real time, experiments to be quickly repeated when mistakes are made or better experimental designs chosen, and the work to be performed outside scheduled class time. Similarly, a simulation of the rat cardiovascular system (both in normal and pithed animals) plays a key role in our cardiovascular system pharmacology course (Figure 1). Here, actual experimentation with a real animal is impractical for large classes in terms of time, resources and ethics. But the simulation is advantageous in any case since it allows the rapid application of a wide range of agonists and antagonists, allowing the roles of different receptor systems to be investigated and disentangled. Students are set a number of tasks aimed at characterising the receptors and systems controlling heart rate and blood pressure; α- and β-adrenoceptors, the renin-angiotensin system, nitric oxide, etc. While simulations are an integral part of our undergraduate teaching, we nevertheless remain committed to providing real experimental work at undergraduate level, ranging from human cardiovascular studies, a variety of pharmacological preparations and cell cytoxicity assays. No simulation (particularly teaching ones) yet delivers the full complexity of even the simplest biological tissue. Neither do simulations develop the range of practical skills and attention to detail necessary to function in the experimental laboratory. However, an appropriate combination of the two allows both the development of skills in basic laboratory techniques and practices, and higher level skills in experimental design, analysis and interpretation, while also providing supportive learning activities in a variety of courses. The simulations discussed here, which have applications both in physiology & pharmacology, are available free of charge and are currently used in a number of departments worldwide. They can be downloaded from http://spider.science.strath.ac.uk/sipbs/page.php?show=software_sims