Different studies, particularly in the United States of America, have shown a positive relationship between religiousness and survival. Few studies conducted in Europe, or in a population of old old respondents, have verified it. This research provides new confirmation of this relationship under the Swiss Interdisciplinary Longitudinal Study on the Oldest Old (N = 340 at baseline), a study following subjects aged 80 to 84 at baseline since 1994. Results of logistic regression analyses indicate that religious practice is positively related to survival in a time interval of 12 to 18 months, controlling for other possible explanatory factors such as functional health or depressive symptoms. Different interpretations of this result are discussed here. To our knowledge, this is the first time that this effect has been demonstrated in a population of old old subjects composed of a large sample of Catholic believers.