Gray snappers were collected from four different habitats and examined for trematodes. The incidence of each trematode was calculated for each habitat during each season. Intermediate hosts of the trematodes were also collected. It was found that the habitat in which gray snappers reside is more important than their size, sex, or the season of the year in determining the nature of their trematode populations. This may be the result of the intermediate host distribution being regulated by the habitat. Seasonal changes in trematode populations result from fish movements, such as spawning migrations or movements in response to cold water. The differences between the trematode populations of large and small snappers probably are a function of their residing in different habitats and eating different organisms. The sex of gray snappers has no discernable [i.e. discernible] effect on their trematode populations. Metadena obscura sp. n. (Cryptogonimidae) was found in the pyloric caeca and intestine of Lutjanus griseus (Linnaeus). Nine species of trematodes were found in the intestine and pyloric caeca of Lutjanus griseus near Lower Matecumbe Key: Metadena globosa, M. adglobosa, M. obscura, Paracryptogonimus neoamericanus, Hamacreadium mutabile, H. gulella, Helicometrina nimia, Helicometra execta, and Stephanostomum casum.