Relations between infant-mother attachment security at 15 months and infants' (N = 206) joint attention behaviors (a) with an experimenter at 8 and 15 months, and (b) with their mothers at 15 months were investigated. No concurrent or longitudinal relations were observed between attachment security and infants' tendency to respond to an experimenter's bids for joint attention. Higher levels of initiating joint attention with an experimenter at 15 months were associated with insecure-avoidant attachment. Insecure-avoidant attachment was also associated with lower scores for initiating high-level joint attention behaviors (pointing, showing, and giving) with the mother at age 15 months. The fact that security-related differences in initiating joint attention with an experimenter were observed only once the attachment relationship was consolidated suggests that (a) attachment security may influence infants' active engagement with new social partners, and (b) insecure-avoidant infants may compensate for reduced social contact with the caregiver by initiating more interaction with other social partners. (Contains 2 tables and 2 figures.)