The responses of adult female blacklegged ticks,Ixodes scapularis Say, to urine from white-tailed deer,Odocoileus virginianus (Zimmermann), belonging to 4 reproductive categories (doe in estrous, doe out of season, reproductive [dominant] buck, young buck) and to a mixture of urine from nondominant bucks in rut, young bucks out of rut, and nonestrous does were studied in laboratory behavioral bioassays. In high humidity (≈95% RH) in a glove box there were no statistically significant arrestment responses to any of the 5 types of urine, but an avoidance response was observed to urine from dominant reproductive bucks. When ticks were tested at ≈50% RH, with samples of all 5 types of urine in the glove box, significant arrestant responses by the ticks were elicited by urine from does in estrous and by dominant reproductive bucks. When tested without other types of urine in the glove box, the urine mixture elicited an arrestant response at 50% RH. In some circumstances, adultI. scapularis may possibly use deer urine as a chemical cue in selecting host-ambush sites.