In both Sweden and South Africa, the science curriculum for the secondary level emphasizes learning about the functioning of the human body. Both curricula also emphasize the importance of living a healthy life. In this paper the focus is on how students’ ideas about the human body are constituted in explanations of three different scenarios, and in what way the students are transferring explanations between these scenarios. The study surveyed 161 9th grade students in five different schools in South Africa, and discusses the results in perspective of a previous study involving 88 students in Sweden. In both countries issues about body and health are discussed in several different subjects in school. The same data collection methods were used in both countries: drawings, written questions (open-ended and multiple-choice items), and interviews with selected students. The questions emerge from three scenarios: what happens in the body when you eat an open sandwich, drink water, and swallow a painkiller. We report that it is difficult for the students to horizontally transfer knowledge of the digestive system to other less well-known scenarios. In comparing the use of three systems in the painkiller-scenario to the horizontal transfer between the sandwich- and the painkiller-scenarios we see that the difference is much less pronounced in South African results compared to the Swedish study. There are more similarities than differences between the results of this South Africa study and results obtained in Europe, but there are also differences especially with regard to non-scientific ideas about the human body.