Abstract : Twenty Bahraini patients with different thyroid disorders were analyzed and the role of several risk factors in the pathogenesis of these disorders was investigated. Among the various risk factors, older age in females appears to be an important factor and may be related to lack of hormones, especially estrogen, during menopause. We found no role for alcohol consumption or hereditary or environmental factors, such as radiation or chemicals, in the pathogenesis of these disorders as the subjects were not exposed to these risks and did not have affected relatives. It is not clear whether smoking or iodine intake have roles in these disorders. The role of activation of several proto-oncogenes and loss of function of the p53 tumor suppressor gene were also investigated in the development of thyroid neoplasms. We found that activation of the ret oncogene by rearrangement was not important in papillary carcinomas or thyroid tumorigenesis in general in the Bahraini population. There may be a role for c-myc, erbB-2, and trk-B activation in the development of some of the thyroid disorders studied. These oncogenes and the p53 tumor suppressor gene seem to be involved in one patient who, according to histological and pathological analysis, had Grave's disease. The relevance of these findings to thyroid tumor development in Bahrain is discussed.