During the Phase I period, Westchester Distribution Systems developed and tested a system which uses hand held computers (HHCs) to facilitate clinical trials of therapeutic drugs. The system is flexible and can be used in a wide range of protocols. The HHC remains with the patient throughout the clinical trial. Its functions include prompting the patient to take medications, administering rating scales, and asking the patient about progress and side effects. It can detect patterns of responses by the patient, and present special prompts when changes in the patient's condition warrant. When the patient visits the clinic, the data from the HHC are unloaded to a personal computer for printout and analysis. During Phase II, the HHC will be used in three clinical trial studies, the determine whether the HHC increases patient compliance with the study protocols, and increases the accuracy and detail of the collected data. Data collected on the HHC will be compared with the data collected through patient interviews during periodic clinic visits. The studies will determine how easy it is for patients and staff to use the system, and the costs involved.