Deer (Odocoileus spp.) can cause substantial damage to agricultural crops, resulting in economic losses for producers. We developed a deer-activated bio-acoustic frightening device to reduce white-tailed deer (O. virginianus) damage in agricultural fields. The device consisted of an infrared detection system that activated an audio component which broadcast recorded distress and alarm calls of deer. We tested the device against unprotected controls in cornfields during the silking–tasseling stage of growth in July 2001. The device was not effective in reducing damage: track-count indices (F_1,4=0.02, P=0.892), corn yield (F_1,9=1.27, P=0.289), and estimated damage levels (F_1,10=0.87, P=0.374) did not differ between experimental and control fields. The size (F_2,26=1.00, P=0.380), location (F_2,25 =0.39, P =0.684), and percent overlap (F_2,25 =0.20, P =0.818) of use-areas of radiomarked female deer did not differ between during- and after-treatment periods. We concluded that the deer-activated bio-acoustic device was not effective in protecting cornfields in this study; however, the device may be more effective in small areas such as gardens or for high-value crops that do not grow tall enough to offer protective cover.