Olfactory communication of dominance status in the hispid cotton rat ( Sigmodon hispidus ) was evaluated by examining the relationship between dominance of individuals and their urinary- and fecal-marking patterns. Their response to presence of urine or feces of con-specifics also was examined. Dominant males, but not females, marked more with urine than did subordinates. Dominance was not associated with fecal marking by either sex. Marking response by males and nonreproductive females to feces of a same-sex opponent was associated with dominance status of the fecal donor. Male response to urine from males also was associated with dominance status of the urine donor. These results indicate that dominance status is communicated by urinary and fecal odors. Marking by nonreproductive females decreased whereas marking by reproductive females increased when exposed to urine from males. Response of reproductive females to feces of either sex was dependent on the dominance status of the female.