Fibropapillomatosis (FP) is a neoplastic disease and a most important cause for stranding and death of the green turtle chelonia mydas. The Chelonid Herpesvirus 5 (ChHV5) is considered its causative agent. Since ChHV5 does not replicate in cell cultures, many questions concerning its pathogenesis and epidemiology, including the prevalence among marine turtles have not been solved. I developed an ELISA for detecting turtle antibodies against two putative ChHV5 envelope glycoproteins (F-US4 and F-US8). To generate standard antisera for cut-off values, I produced soluble fragments of these antigens with the aim of using them as immunizing antigens in hatchling turtles. To ask from which age on hatchlings would be immunocompetent, I developed a second ELISA, suitable for detecting IgY in turtle sera. It took several months for them to become capable of mounting antibody responses. Therefore, the immunization experiments could not be completed within the time frame of my thesis. I tested a panel of sera collected from Australian and Hawaiian green turtles with or without FP for antibodies against F-US4 and F-US8. I detected only a few animals (almost exclusively with severe FP) with considerable amounts of antibodies against these two antigens and only few animals without FP were identified as carriers of antibodies against ChHV5 antigens. My data do not agree with the present views concerning the causative link between FP and ChHV5 as well as the natural reservoir of ChHV5.