Latrine behavior, or the preferential, repeated use of 1 or more specific defecation sites, is well known among mammals and believed to function in olfactory communication among individuals or groups in many circumstances. Primates have reduced their capacity for olfaction in favor of more developed visual systems; however, several prosimian primates regularly use olfactory communication for transmission of social signals, most often using scent gland secretions and urine. Latrine behaviors have been described rarely in primates and have traditionally not been included in reviews of primate olfactory communication, yet we found ample evidence that certain primate species habitually use latrine sites for defecation. Here we review the previous evidence for latrine use in primates and report new and more extensive observations of latrine use in 2 lemuriform primates (Lepilemur sp. and Hapalemur griseus). Based on these new observations, we present and evaluate 4 available hypotheses for the function of latrines (advertisement of sexual cycling, predation avoidance, intragroup spacing, and intergroup resource defense) in lemur taxa for which sufficient evidence of latrine use exists. In all cases, intergroup resource defense is the function most consistent with available observations.