This study examined the relationship between parental experience, parental knowledge, and the development of extremely low birth weight infants. The subjects (N = 40) were extremely high-risk infants averaging 1000.0 grams birthweight and 28.1 weeks gestational age. The study found that mothers of preterm infants called upon the same types of experiences and sources of information about infancy as mothers of full-term infants. Further, ratings of maternal accuracy on the Knowledge of Infant Development Inventory accounted for 13% to 15% of the variation on the Mental Development Index (MDI) and Psychomotor Development Index (PDI) of the Bayley Scales of Infant Development at 8 months corrected age. The infants of mothers with greater than average knowledge about infancy scored approximately one standard deviation higher on both the MDI and the PDI than did the infants of mothers who had less than average knowledge about Infancy. Implications for intervention are discussed.