A retrospective cohort study was conducted to identify risk factors associated with children lost to care, and their families, compared to those not lost to care within the California Early Start Program. The cohort included data on 8987 children enrolled in the Early Start Program in 1998. This cohort consisted of 2443 children lost to care, 6363 children not lost to care, and 187 children that were lost to follow-up due to death or moving outside the state of California. Premature birth was the only medical risk factor in this study related to an increased risk of loss. Family risk factors exert a significant effect on loss to care. Risk factors that are predictive of loss to care include mother's age and educational level, Medi-Cal ineligibility, and lack of transportation. By identifying and examining risk factors for loss to care, interventions may be strengthened to promote continued family participation in early intervention services. (Contains 4 tables.)