The basis of olfactory signatures mediating human kin recognition was investigated in two experiments. The odors of mothers and offspring were correctly matched (by subjects unfamiliar with the stimulus individuals) at a greater than chance frequency. In contrast, subjects were not able reliably to match the odors of husbands and wives. These data support the hypotheses that characteristic individuals odors are genetically mediated and that kin recognition should be facilitated by the similarity of such familiar odors among close relatives.