ABSTRACT: Fibropapillomatosis is a neoplastic disease that is commonly found in the green turtles Chelonia mydas in tropical and subtropical regions of the world. In the current project, juvenile green turtles were captured with large-mesh tangle nets in the Indian River Lagoon and on nearshore reefs of Indian River County, Florida, USA, in 1998 and 1999. The purpose of the study was to determine the relationship between the severity of the disease and the general health of green turtles as indicated by blood parameters. All turtles were measured and examined, and the overall severity of the disease was rated by the size, number, and location of external fibropapilloma tumors. Hematocrit, total protein, and hemoglobin concentration were measured and compared with tumor scores (tumor severity appraisal). As the tumor score increased, the blood parameters of turtles decreased; for instance, the percentage of decrease in hematocrit for mildly afflicted, moderately afflicted, and severely afflicted groups were 2.6, 18.3, and 45.5%, respectively. Severely afflicted turtles suffered from anemia, while individuals with mild affliction did not.