We aimed to evaluate the effects of environmental doses of perfluorooctanoic acid (PFOA) on bioconcentration and gene expression in common carp. Adult male and female carp were exposed to environmental (200ng/L) and experimental (2mg/L) doses of PFOA for 56 days. Carp exposed to 200ng/L had levels of PFOA below the level of detection in all tissue samples analyzed, whereas variable concentrations were measurable in various tissues from carp exposed to 2mg/L. The expression level of the glutathione-S-transferase gene, coding for a detoxifying enzyme, increased in a PFOA-dose dependent manner in liver tissues from 200ng/L to 2mg/L exposure (p<0.05). The expression levels of CYP19A gene, coding for the enzyme that converts testosterone into estrogen, were altered in gonadal tissues from male and female carp exposed to either 200ng/L or 2mg/L; expression increased in male gonads and decreased in female gonads. Unexpectedly, the expression levels of CYP19A in male and female gonads from carp exposed to 200ng/L or to 2mg/L were similar (p>0.05). Therefore, even though environmental doses of PFOA did not accumulate in tissues of the common carp, they did affect the gene expression levels of glutathione-S-transferase in the liver and CYP19A in the gonads. These observations raise concerns that exposure to environmental doses of PFOA may affect gene expression in animals and, possibly, in humans, with important health consequences. This article is protected by copyright. All rights reserved.