ObjectivesThe monitoring of medication compliance in clinical trials is important but labor intensive. To check medication compliance in clinical trials, a system was developed, and its technical feasibility evaluated.MethodsThe system consisted of three parts: a management part (clinical trial center database and a developed program), clinical trial investigator part (monitoring), and clinical trial participant part (personal digital assistant [PDA] with a barcode scanner). The system was tested with 20 participants for 2 weeks, and compliance was evaluated.ResultsThis study developed a medication compliance monitoring system that used a PDA with a barcode scanner, which sent reminder/warning messages, logged medication barcode data, and provided compliance information to investigators. Registered participants received short message service (SMS) reminder/warning messages on their PDA and sent barcode data at the dosing time. The age range of the participants was 29 to 73 years. Five participants were <50 years old and 8 were ≥65 years old. The total mean compliance rate was 82.3%. The mean compliance rate was 83.1% in participants <65 years old and 81.1% in those ≥65 years old.ConclusionsThe system was feasible, usable, and effective, even with elderly participants, for monitoring medication compliance in clinical trials using a PDA with a barcode scanner, and may improve the quality of clinical trials.