Survival in old age has been shown to be positively related to religiousness, and in particular to church attendance. This research provides new confirmation of this relationship under the Swiss Interdisciplinary Longitudinal Study in 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 participation in church services or a composite measure of religiousness comprising participation in services and the frequency of prayer is positively related to survival in a time interval of 12 to 18 months, controlling for other possible explanatory factors such as functional helath or depressive symptoms. To our knowledge, this is the first time that this effect has been demonstrated in a population of old old subjects and in a Latin country of Europe where the number of Catholic subjects is high.