From January to April 1984, 63 Rattus rattus and 40 R. norvegicus were trapped in northeastern Puerto Rico and examined for Angiostrongylus cantonensis adults. Nineteen (47.5%) of the R. norvegicus and 10 (15.9%) of the R. rattus were infected, giving an overall infection rate of 28.2%. Four species of terrestrial snails and one species of brown slug were examined for A. cantonensis larvae. Two snail species, Subulina octona and Aquebana belutina, were found infected with third stage larvae of A. cantonensis. These larvae were harvested and inoculated per os into adult white mice. Immature adult worms were found in the brain tissue of all mice inoculated. This is the first report in the rat and snail populations of Puerto Rico.