At normal atmospheric pressure, an erucic acid-supplemented diet produces an increase of heart mitochondrial triglycerides. With the same quantity of erucic acid, hypoxia emphasizes the triglyceride overload in rat heart mitochondria. Thus, hypoxia increases the risk caused by rapeseed-oil. In hypoxia or at normal atmospheric pressure, rapeseed-oil without erucic acid does not modify the level of mitochondrial triglycerides.