Very low birth weight preterm infants randomized to receive comprehensive primary care in an ongoing clinical trial were prospectively evaluated to determine the cause of frequent emergency room use despite the availability of a primary healthcare provider and specific social services. Mothers were interviewed to assess knowledge of available resources, when to seek medical attention, and the perception of problems that limit access to health care. The healthcare provider was not called before 49% of the emergency room visits and mothers often did not recall what infant signs needed medical attention. Seventy-nine percent of emergency room visits were delayed more than 10 hours; and 15 of 62 (24%) emergency room visits resulted in admittance to the hospital. We conclude that in high-risk populations, the mere availability of primary care does not assure that it will be used. New strategies to help parents know when and how to use services are needed to increase the delivery of primary care.