BACKGROUND Research suggests an increased type II diabetes mortality risk among workers occupationally exposed to PFOA. However, a cross-sectional study of highly exposed Mid-Ohio Valley community residents did not demonstrate an association between PFOA and type II diabetes. OBJECTIVES We examined the relationship between exposure to PFOA over time and incidence of type II diabetes in a cohort of community residents and workers exposed to high levels of PFOA via contaminated drinking water. METHODS Community residents and workers were interviewed in 2008-2011 to obtain medical history and other demographic information. Cumulative serum PFOA exposure estimates were calculated based on residence and occupation locations, and a history of plant emissions. We estimated the risk of developing type II diabetes using Cox proportional hazard models, controlling for demographic characteristics and family history. RESULTS Out of 32,254 survey respondents, there were 4434 cases of self-reported type II diabetes, of which 4129 were validated through medical record review. In analyses based on validated type II diabetes, there was no trend of increased risk with increased cumulative PFOA serum levels (HRs compared to lowest exposure decile: 0.91 (95% CI: 0.76-1.08), 1.18 (95% CI: 0.99-1.40), 0.96 (95% CI: 0.81-1.15), 1.04 (95% CI: 0.87-1.24), 1.11 (95% CI: 0.93-1.32), 1.06 (95% CI: 0.89-1.26), 1.00 (95% CI: 0.85-1.19), 1.03 (95% CI: 0.86-1.23), 1.01 (95% CI: 0.84-1.20)). There was no association between fasting glucose level and cumulative serum levels of PFOA, after excluding diabetics. CONCLUSIONS We do not find an association between PFOA exposure and incidence of type II diabetes.