We investigated the responses of the wood mouse ( Apodemus sylvaticus ) and bank vole ( Clethrionomys glareolus ) to odor in traps by examining the capture rate of live-traps with respect to their immediate trapping, and therefore semiochemical, history. Both bank voles and wood mice preferred traps previously occupied by conspecifics. However, bank voles showed no sexual bias to this preference, whereas wood mice exhibited a significant preference for traps that had been occupied by members of the opposite sex. In accordance with current theories on their breeding system, wood mice showed sexual differences, both in their reaction to the odor of members of the same sex and in the temporal nature of their reaction to conspecific odor. Wood mice also avoided traps that had previously held bank voles. The results indicate that live-trapping data may reveal important semiochemical interactions between both heterospecific and conspecific animals and highlight the need for caution, both in the deployment of traps and the analysis of data, when using such techniques for the enumeration of populations.