This descriptive correlational study investigated the reliability of a new measure of client-nurse practitioner interaction, the Client Encounter Form (CEF), and used the CEF to describe the domains of client-nurse practitioner interaction that occurred during problem and preventative visits at a primary care clinic. The CEF is based on Cox's Interactional Model of Client Health Behavior. Data were collected from a convenience sample of 41 primary care clinic visits. Descriptive data on all clients and the patterns of use characterized by the CEF were collected using retrospective chart review (n = 60). Reliability testing showed the CEF has high interrater reliability; Cohen's Kappas for its dimensions ranged from 0.78-1.0. The CEF was also shown to be useable in a primary care clinic. Health information, affective support, goal setting, and technical procedures were consistently part of the nurse-client interactions in this sample, demonstrating they are part of the nurse practitioner model of care. Analysis revealed different patterns of interaction for preventative and problem-oriented visits. Preventative visits had higher levels of health promotion information, psychological affective support, and health promotion goal-setting behaviors. Problem visits included more information regarding the client's diagnosis, medications, and treatments, and more affective support related to the client's physical condition.