Field investigations were performed over a 2- or 3-year period at five sites in central France to determine the prevalence of Haplometra cylindracea infection in three species of adult Lymnaea, and to compare it with that of Fasciola hepatica infection recorded in the same snails. L. glabra, L. palustris, and L. truncatula harboured Haplometra larval forms but the prevalence of this infection varied according to the site and snail species studied. The prevalences in May ranged over 0-66.9% in L. glabra, 3-7.7% in L. palustris, and 0-31.5% in L. truncatula. The mean intensity of H. cylindracea infection in May did not show any significant variation, whatever the site and species studied. The prevalence of F. hepatica infection was significantly lower in snails collected in sites known for H. cylindracea infection than in those originating from nearby meadows (0-1% instead of 1-5%). H. cylindracea could develop in some Lymnaea species and its occurrence had an impact in snails by decreasing the prevalence of F. hepatica infection.