The influence of water vole Arvicola terrestris scherman fluctuations on red fox Vulpes vulpes reproduction was investigated in a central European mountainous habitat. We also examined the relationship between annual variations in the mean body weight of the cubs and trophic changes. Water vole abundance was estimated by seasonal trappings, and fox families and cubs were counted every spring. The number of fox families differed little between years, and the differences were not related to water vole abundance. Mean litter size also varied from year to year, but independently of water vole densities. No relation was found between the weight of the cubs and water vole supply. The lack of any significant annual variations in fox breeding success means that despite the low availability of wild alternative prey, foxes found suitable trophic conditions in the absence of water voles. Moreover, as suggested by the increase in the consumption of food scraps by foxes during vole lows, man has certainly been instrumental in preventing a decrease in fox breeding success at the low stage of the water vole cycle.