Amyloidosis is associated with the deposition of amyloid substance in various tissues of the body. In several forms of familial amyloid polyneuropathy, mutated transthyretin is the main fibril component. The disease is inherited as an autosomal dominant trait with onset in adult life, but few carriers develop symptoms. The aim of the present investigation was to screen for additional factors that might be necessary for the development of familial amyloid polyneuropathy. We conducted a case-control study involving 51 male and 30 female cases of clinically overt familial amyloid polyneuropathy and 306 male and 317 female population controls. We considered occupational exposures, disease histories, and medical treatments as potential determinants of risk for clinically overt disease. We found an odds ratio of 5.4 for dressmakers. Low and high levels of exposure to organic solvents resulted in an odds ratio of 2.1 and 11.8, respectively. A history of prostatic hyperplasia, cholecystic disease, or appendectomy was also a risk factor, possibly as a consequence of anesthesia.