The delivery of primary health care involves complex interactive communication between the provider and patient. Describing the manner or style of this communication is important to more completely understand the delivery of primary health care. The purpose of this study was to examine provider's style of interaction with the patient and to compare the styles of nurse practitioners and physicians in joint practice. A total of 412 provider/patient clinic visits including 276 with physicians and 136 with nurse practitioners were videotaped and analyzed using a content-based interactive analysis system. Five provider style dimension indices were constructed including affiliation, control, somatic, psychosocial, and information indices. The results of this study show that the development of a content-based interactional analysis system which focuses on clinician activities can be useful in describing important aspects of the provider/patient encounter. Overall, there was little difference between nurse practitioner and physician style of interaction. Nurse practitioners, however, exhibited significantly more concern with psychosocial issues than physicians. Type of visit and visit history were also factors associated with provider style. Using the style dimension indices constructed for this study a typology of provider styles was developed.