Context: Mild abnormalities of thyroid function have been associated with both beneficial and detrimental effects on mortality. Objective: Our objective was to determine the association between continuous TSH as well as categories of thyroid function with total and cause-specific mortality in a cohort of older men. Design, Setting, and Participants: Data were analyzed from the Osteoporotic Fractures in Men (MrOS) study, a cohort of community-dwelling U.S. men aged 65 yr and older. A total of 1587 participants randomly selected for thyroid function testing were included in this analysis. TSH and free T 4 were measured at baseline, and four categories of thyroid function were defined. (subclinical hyperthyroid; euthyroid; subclinical hypothyroid TSH <10 mIU/liter; and subclinical hypothyroid, TSH ≥10 mIU/liter.) Main Outcome Measure: Total mortality, cardiovascular (CV) and cancer deaths were confirmed by review of death certificates. Results: There were 432 deaths over a mean follow-up of 8.3 yr. In fully adjusted models, there was no association between baseline TSH and any death [relative hazard (RH)=1.01 per mIU/liter,95% confidence interval (CI) = 0.95-1.06], CV death (RH = 1.05 per mIU/liter, 95% CI 0.96-1.15), or cancer death (RH=0.96 per mIU/liter,95%CI=0.85-1.07). Therewasalsonostatistically significant association between thyroid function category and total or cause-specific mortality, but few men (n = 8) had subclinical hypothyroidism with TSH levels of 10 mIU/liter or higher. Conclusions: A single measurement of thyroid function did not predict total or cause-specific mortality in this cohort. These data support neither a beneficial nor a detrimental effect of subclinical thyroid dysfunction in older men. Summary: Subclinical thyroid dysfunction is not associated with an increased risk of all-cause or CV mortality in older men.