This study examined the development of joint attention in 95 infants assessed between 9 and 18 months of age. Infants displayed significant test-retest reliability on measures of following gaze and gestures (responding to joint attention, RJA) and in their use of eye contact to establish social attention coordination (initiating joint attention, IJA). Infants displayed a linear, increasing pattern of age-related growth on most joint attention measures. However, IJA was characterized by a significant cubic developmental pattern. Infants with different rates of cognitive development exhibited different frequencies of joint attention acts at each age, but did not exhibit different age-related patterns of development. Finally, 12-month RJA and 18-month IJA predicted 24-month language after controlling for general aspects of cognitive development.