As in other European countries, the religious landscape of Switzerland has diversified over the last forty years, with a movement away from the traditional institutions and a rapid expansion of minority religions. Taking advantage of the Swiss statistical system, which records residents’ religion in the census and in vital records, the mortality differentials over the period 1991-2004 are analysed according to self-reported religious affiliation. Using record linkage techniques, it is possible not only to assess the quality of these data with a view to correcting aggregate estimates, but also to adopt an individualized and multivariate approach to the relation between religion and mortality by cause of death. The analysis reveals significant survival differentials between religious groups, probably linked to differences in lifestyle. A sociological interpretation of the results supports the hypothesis of a mortality gradient by degree of religiosity in Switzerland.