Medication adherence behaviors of 61 elderly adults were examined using a sensitive microelectronic monitoring device. To assess the effects of external cognitive supports on adherence, different subjects received (a) no intervention, (b) an organizational chart, (c) an over-the-counter medication organizer, or (d) both the chart and organizer. The young-old subjects showed a high rate of adherence (94%) and were not improved by the addition of the interventions. Old-old subjects had a lower rate of adherence (85%) than young-olds. Omission errors were the most frequent mistakes and were lower in the condition in which subjects received both chart and organizer.