A common polymorphism (Val158Met) in the gene encoding for the catechol-O-methyltransferase (COMT) enzyme has been associated with differences in prefrontal cognitive function in schizophrenic patients and healthy adults. While several studies indicate that the Met allele is associated with better performance on measures of executive function, working memory and verbal fluency, results have been inconsistent. Furthermore, fewer studies have investigated this relationship in older adults, a group known to experience impairments in prefrontal cognitive functions. Additionally, findings vary according to the gender distribution of study participants. Keywords Catechol-O-methyltransferase; cognition; older adults; genderWe examined whether COMT genotype interacted with gender to impact cognition in a cohort of 163 healthy, older adults. Memory, verbal ability and areas of prefrontal cognitive function, including attention, speed-of-processing, and executive function, were assessed. We found no significant association between COMT genotype and any cognitive measure. However, gender interacted with COMT genotype to impact cognitive performance. Males homozygous for the Val allele performed better than both the Val/Met and Met/Met groups on measures of delayed recall. Heterozygous women performed better than their homozygous counterparts on the measure of verbal ability. These findings suggest that gender may be an important variable in consideration of the impact of COMT on cognition. Further, when gender is taken into consideration, any negative impact of COMT genotype may extend to cognitive domains other than those associated with prefrontal regions.Cognitive impairment in older adults is well-documented and several genetic markers have been proposed to moderate this effect [28]. One genetic marker documented to impact cognitive functioning is COMT, the gene that codes for catechol-O-methyltransferase, a critical enzyme in the metabolic degradation of dopamine in the prefrontal cortex. This gene, mapped to Address correspondence to Ruth O'Hara, Ph.D.,