Asymptomatic and partially symptomatic Alzheimer's disease (APSYMAD) are a series of cognitive states wherein subjects have substantial Alzheimer's disease (AD) pathology (classification B or C by the Consortium to Establish a Registry for AD criteria), but have normal or only partially impaired cognitive function; all of these subjects are non-demented. These cognitive states may arise from the prevention or delay of clinical symptom expression by exposure to certain nutritional factors. This study examined blood levels of folate and antioxidants (i.e., carotenoids) in relation to APSYMAD, nested in the Nun study, a longitudinal study of aging and AD. Sixty elderly female subjects, who had AD on the basis of neuropathology exams, were included. Following adjustment for APOE4 status, education level, and age at blood draw, subjects with the highest blood folate levels had a higher likelihood of being in the APSYMAD group as compared to the demented (AD) group (odds ratio = 1.09, 95% CI = 1.00-1.18. p < 0.06). This association was not significantly influenced by additional adjustment for blood concentrations of carotenoids. Restriction of the population to subjects with near normal cognition on the cognitive state score (score = 1-3) indicated an elevated association with blood folate (odds ratio = 1.12, 95% CI = 1.01-1.25, p < 0.04). Blood carotenoids were not associated with APSYMAD. Thus, folate status may influence the expression of clinical symptoms of AD disease and aid in the delay or prevention of dementia.