Although most psychological assessments are based on measures related to an individual’s average level of performance, it has been proposed that measures of variability around one’s average may provide unique individual difference information and have clinical significance. The current study investigated properties of within-person variability in measures of performance accuracy in a sample of more than 1,700 healthy adults. Contrary to what has been reported with measures of within-person variability in reaction time, measures of within-person variability in performance accuracy from different cognitive tests had weak correlations with one another, very low stability across time, and near-zero correlations with longitudinal change in cognitive abilities.