Introduction. Chemotherapy-associated executive dysfunction is an adverse effect of conventional antineoplastic treatment that affects many patients. It has been reported that the presence of specific polymorphisms in key genes can cause a greater susceptibility to develop this condition. Objective. To determine the relationship between the Val66Met polymorphism (196 G>A) of the BDNF gene and the development of executive dysfunction in female patients with breast cancer treated with chemotherapy. Methods. 73 female breast cancer patients were evaluated for executive dysfunction before and after chemotherapy. The evaluation was carried out with the INECO Frontal Screening test (IFS). The genotype (GG=Val/Val, GA=Val/Met and AA=Met/Met) was determined by PCR and sequencing of BDNF gene. Association analysis was performed by calculating the Odds Ratio (OR) and by quantitative comparison. Re...