The purpose of this study was to develop and pilot-test an instrument that determines the relationship between perceptions, intended use, and actual use of the personal digital assistant (PDA) by primary care physicians for drug information access and prescribing. The instrument studied addressed human factor limitations, attitudes toward learning to use the PDA, and fear of losing either confidential information or the PDA itself. The study instrument was intended to differentiate between applications a physician will or will not incorporate into daily practice and to predict which physicians are more likely to successfully adopt use of a PDA. A 63-item survey was administered at baseline to 78 primary care physicians, randomized into control and intervention groups. The physicians in the intervention group were provided a PDA with electronic prescribing software and drug information software, training in the use of the device and the software, and an infrared printer to write prescriptions. They were then asked to prescribe using the PDA or by hand, as they preferred. The control group physicians continued traditional handwritten prescribing and accessed their usual drug information sources. The survey was readministered to both groups after they had completed 500 prescriptions. Postintervention data did not support ready acceptance of the PDA as a prescribing device; however, the physicians did find the PDA useful for accessing drug information at the point of care. Potential factors that predict physician use of the PDA were learning-related attitudes, human factor limitations, and concerns about loss of confidential and critical information.