BioUD with the active ingredient 2-undecanone originally derived from wild tomato plants is a new repellent recently registered by the US EPA. Repellent efficacy of BioUD (7.75% 2-undecanone) and DEET (98.11%) was examined in the laboratory using a choice test between repellent-treated and control filter paper surfaces for Amblyomma americanum, Dermacentor variabilis, and Ixodes scapularis. BioUD provided greater repellency against A. americanum and I. scapularis than DEET. No difference was found between BioUD and DEET against D. variabilis. In head-to-head assays between BioUD and DEET, undiluted and 50% dilutions of BioUD were more repellent than undiluted DEET against all three species tested. Similarly, a 25% dilution of BioUD was more repellent than DEET against A. americanum while no difference in mean percentage repellency was found between a 25% dilution of BioUD and DEET against I. scapularis. Based on regression analysis, the concentration of BioUD required for equivalent repellency to 98.11% DEET was 39.5% for D. variabilis and 29.7% for I. scapularis. A log-probit model could not be constructed for A. americanum from the dosages tested. Based on filter paper head-to-head assays, BioUD is at least 2-4 times more active as a repellent than DEET against three species of ixodid ticks under the conditions of our laboratory bioassays.