The author has studied the reproductive potencial of 3 species of Planorbidae, Biomphalaria glabrata, B. tenagophila and B. straminea from March to April 1978. The data were recorded daily. Eggs-masses of 20 snails of each species were obqerved. The number of egg-masses and the number of eggs in each were counted. The statistical test showed that the samples of B. glabrata exhibited a larger reproductive potencial than the other species. The smallest reproductive potencial was attribuited to B. tenagophila.