This report describes the development of the Perceived Involvement in Care Scale (PICS), a self-report questionnaire for patients, and its relation to primary care patients' attitudes regarding their illnesses and the management of them. The questionnaire was administered to three independent samples of adult primary care patients. Patients' satisfaction and their attitudes regarding their illnesses are evaluated after their medical visits. This instrument is designed to examine three relatively distinct factors: 1) doctor facilitation of patient involvement, 2) level of information exchange, and 3) patient participation in decision making. Of these factors, doctor facilitation and patient decision making were related significantly to patients' satisfaction with care. Doctor facilitation and information exchange related consistently to patients' perceptions of post-visit changes in their understanding, reassurance, perceived control over illness, and expectations for improvement in functioning. The role of physicians in enhancing patient involvement in care and the potential therapeutic benefits of physician facilitative behavior are addressed.