Beneficial health effects of cranberries (CBs) and wild blueberries (BBs), such as reduced levels of oxidative stress, have been demonstrated in feeding studies. These Vaccinium berries contain high levels of flavonoids; however, the bioavailability of flavonoids is generally low. We investigated the in vitro effects of these berries on intestinal cells, focusing on mitigating oxidative stress and associated reactive oxygen species (ROS). First, we simulated the passage of CB and BB through the gastrointestinal (GI) tract by treating berry homogenates to a battery of digestive enzymes. Then, Caco-2 cells, a model of small intestine epithelial uptake, were exposed to these homogenates for 60 min. Using a cell-free assay, we found that the antioxidant activity in CB homogenates was not affected by these enzymes, but that BB homogenates treated with gut enzymes had 43% lower free-radical quenching activity (P