Abstract It was hypothesized that the frequent application of synthetic odors to squirrel monkey mothers ( Saimiri sciureus) could affect filial attachment independently of odor preferences by their infants. Six control infants were reared by mothers who retained naturally produced odors, and 12 experimental infants were reared by mothers who were regularly sprayed with a synthetic odor. In the first experiment, control but not experimental animals preferred their mother to a stranger during monthly visual discrimination tests in Months 1–5 postpartum. In the second experiment, infants preferred their synthetic rearing odor to an unfamiliar synthetic odor, but only in Month 5. The results suggest that the frequent perception of alien odors on the mother may diminish a squirrel monkey infant's behavioral attraction to her in spite of a preference developed for an early rearing odor.