More and more travelers are exposed to high altitude, for example, 176'000 trekkers/climbers were registered in Nepal in 2017. Individual predispositions, a history of altitude illness, the existence of risk factors and/or comorbidities increase the risk of developing specific altitude-related diseases that are potentially life threatening. Nevertheless, the prediction of these diseases remains difficult, especially in subjects without prior exposure to high altitude. In this context different altitude simulation tests have been developed. Their indication, practice and validity are summarized in this article.