Effects of varying olfactory cues on the behavior of domestic male mice (Mus musculus) towards territorial boundaries were studied. Territories were established by three pairs of ♂♂ in a 154 times 86 times 10 cm Plexiglas pen with a moveable floor. After establishment of territories, the floor was shifted 19 cm a total of 21 times on different days. After 13 of these shifts the floor was subsequently covered with perforated sheet metal. In all 8 of the uncovered shifts, and in 8 of the 13 covered shifts, the mice behaved as though the boundary was moved in the predicted direction and distance. The results indicate that mice can use olfactory cues to recognize territorial boundaries.