The practice activities of nurse practitioners (NPs) in primary care have not been well delineated. The purpose of this study is to identify the activities of NPs in the provision of primary care. Patient, practitioner, and healthcare system variables were collected to describe the sample and determine if these factors influenced the activities of NPs. Primary care NPs (n = 139) representing the practice areas of pediatrics (n = 12), family (n = 75), adult (n = 15), and women's health (n = 37) responded to serial questionnaires using Delphi technique asking them to identify activities they perform routinely in their practices. Using frequency analysis, activities common to the practice of all NPs were identified, and using Chi-square, activities of specialty NP practice were identified. Regression analysis was used to correlate NP, patient, and healthcare system variables with the activities performed as part of NP practice. Three lists of activities of NP practice were developed: core activities of all NP practice, specialty activities, and other activities. Initial analyses of variables that might influence NP practice were examined. These results can be useful to healthcare consumers choosing providers, as well as legislators, educators, employers of NPs, and other interested healthcare professionals.