Six measures of systemic iron metabolism were used to predict mortality among 103 patients with Parkinson's disease and 353 controls followed in a longitudinal study. Adjusting for gender, education, ethnicity, presence of dementia, and extrapyramidal signs, transferrin receptor concentration was strongly associated with mortality in patients with PD but not controls. This increase in serum transferrin receptor concentration before death suggests that the previously observed perturbation in iron metabolism continues throughout the disease course.