Base-jumping—jumping off buildings, etc.—is a recent activity derived from skydiving. From participant observation and interviews conducted among base-jumpers in southeastern France, the authors describe this informal sport and the meaning given to it by those who practice it. The observation of this extreme sport where any error has immediate consequences reveals the constant preoccupations of base-jumpers on safety and their permanent temptation to test the limits of the possible. This combination of seriousness and play makes base-jumping a hazardous experience. Faced with danger, base-jumpers try to neutralize the element of chance inherent in any jump. They know that they have no second chance and do not deny the presence of risk.