We studied the function of cheek-rubbing in golden marmots (Marmota caudata aurea) by combining observations of the external morphology of the orbital gland, observational studies of marmots cheek-rubbing, and experimental studies of marmots’responses to olfactory secretions from the orbital gland. Adult males had larger eyepatches–areas without hair above the orbital gland–than adult females. Both sexes produced sufficient glandular exudate to pool on the surface of the skin or fur above the orbital gland. Adult males cheek-rubbed more than adult females throughout the summer active season, but both males and females generally cheek-rubbed within 10m of a main burrow. Adult males responded more vigorously to the smells of non-group members of both sexes than to group members of either sex. Adult females responded more vigorously to the smell of non-group females than to non-group males or group members of either sex. Our results are consistent with the hypothesis that marmot cheek-rubbing functions to mark defended areas, possibly to minimize costs of aggressive interactions.