Plasma levels of anticonvulsants and medical record review were used to assess the drug delivery system (compliance), appropriate dosage, and utilization of plasma level data in 94 institutionalized epileptic children and adults. A two-phase study design was used, with the introduction of plasma level data marking the onset of the second phase. Unexpectedly, the availability of plasma level data on two occasions did not produce appropriate changes in compliance or dosage adjustments (based on chemical criteria) that were clearly needed. From these results we conclude that the overall drug delivery system is inadequate, that inappropriate anticonvulsant doses are used, and that plasma level information on anticonvulsants is underutilized for many of these institutionalized epileptic patients.